Remove final dot after URL to ensure the link is clickable

See #3321 (comment)

Author: eregon

spec/truffle/java_exception_spec.rb

@@ -16,7 +16,7 @@
     out.should == <<-EOS
 
 truffleruby: an internal exception escaped out of the interpreter,
-please report it to https://github.com/oracle/truffleruby/issues.
+please report it to https://github.com/oracle/truffleruby/issues
 
 ```
 custom message (java.lang.RuntimeException)
@@ -40,7 +40,7 @@
     out.should == <<-EOS
 
 truffleruby: unexpected internal exception in at_exit,
-please report it to https://github.com/oracle/truffleruby/issues.
+please report it to https://github.com/oracle/truffleruby/issues
 
 ```
 custom message (java.lang.RuntimeException)
@@ -64,7 +64,7 @@
     out.should == <<-EOS
 
 truffleruby: an internal exception escaped out of the interpreter,
-please report it to https://github.com/oracle/truffleruby/issues.
+please report it to https://github.com/oracle/truffleruby/issues
 
 ```
 message (java.lang.RuntimeException)

src/main/java/org/truffleruby/language/backtrace/BacktraceFormatter.java

@@ -380,7 +380,7 @@ public static void printInternalError(RubyContext context, Throwable throwable,
         final BacktraceFormatter formatter = context.getDefaultBacktraceFormatter();
         stream.println();
         stream.println("truffleruby: " + from + ",");
-        stream.println("please report it to https://github.com/oracle/truffleruby/issues.");
+        stream.println("please report it to https://github.com/oracle/truffleruby/issues");
         stream.println();
         stream.println("```");