Merge bitcoin#28611: Adjust Gradle properties to fix apk build

5f50406 Adjust Gradle properties (Hennadii Stepanov)

Pull request description:

  On the master branch @ d2b8c5e, building the `apk` target fails:
  ```
  $ make -C src/qt apk
  ...
  > Task :compileDebugJavaWithJavac FAILED
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/QtActivityDelegate.java:690: error: cannot find symbol
                  Display display = (Build.VERSION.SDK_INT < Build.VERSION_CODES.R)
                                                                                ^
    symbol:   variable R
    location: class VERSION_CODES
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/QtActivityDelegate.java:692: error: cannot find symbol
                          : m_activity.getDisplay();
                                      ^
    symbol:   method getDisplay()
    location: variable m_activity of type Activity
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/QtActivityDelegate.java:833: error: cannot find symbol
          float refreshRate = (Build.VERSION.SDK_INT < Build.VERSION_CODES.R)
                                                                          ^
    symbol:   variable R
    location: class VERSION_CODES
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/QtActivityDelegate.java:835: error: cannot find symbol
                  : m_activity.getDisplay().getRefreshRate();
                              ^
    symbol:   method getDisplay()
    location: variable m_activity of type Activity
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/QtLayout.java:95: error: cannot find symbol
          Display display = (Build.VERSION.SDK_INT < Build.VERSION_CODES.R)
                                                                        ^
    symbol:   variable R
    location: class VERSION_CODES
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/QtLayout.java:97: error: cannot find symbol
                  : ((Activity)getContext()).getDisplay();
                                            ^
    symbol:   method getDisplay()
    location: class Activity
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/ExtractStyle.java:418: error: cannot find symbol
              if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q)
                                                             ^
    symbol:   variable Q
    location: class VERSION_CODES
  /home/hebasto/git/gui/src/qt/android/src/org/qtproject/qt5/android/ExtractStyle.java:421: error: cannot find symbol
                  numStates = stateList.getStateCount();
                                       ^
    symbol:   method getStateCount()
    location: variable stateList of type StateListDrawable
  Note: Some input files use or override a deprecated API.
  Note: Recompile with -Xlint:deprecation for details.
  8 errors

  FAILURE: Build failed with an exception.

  * What went wrong:
  Execution failed for task ':compileDebugJavaWithJavac'.
  > Compilation failed; see the compiler error output for details.

  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

  * Get more help at https://help.gradle.org

  Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
  Use '--warning-mode all' to show the individual deprecation warnings.
  See https://docs.gradle.org/6.6.1/userguide/command_line_interface.html#sec:command_line_warnings

  BUILD FAILED in 827ms
  ...
  ```

  Fixing it by updating the Gradle tool's properties.

ACKs for top commit:
  fanquake:
    ACK 5f50406 - seems fine.

Tree-SHA512: 52e59fe1c69841370ce2eb670f3618182bf2843582074af4895b8ecb6e5f70dc3fe4eecbffa212efaa534b423ced5b75020f6f09917b52f452121c1e55fbcaac

Author: fanquake

src/qt/android/gradle.properties

@@ -1,4 +1,4 @@
-androidBuildToolsVersion=28.0.3
-androidCompileSdkVersion=28
+androidBuildToolsVersion=30.0.3
+androidCompileSdkVersion=30
 qt5AndroidDir=new File(".").absolutePath
 org.gradle.jvmargs=-Xmx4608M