[SYCL][Doc] Remove outdated CTS config instructions (#6334)

DPC++ implementation has been renamed in Khronos SYCL-CTS project from
Intel_SYCL to DPCPP. These instructions are outdated for 10 months
already.

Khronos SYCL-CTS README file provides updated instructions and this
guide already refers to the README file, so removed part duplicates the
information.

Fixed linked to the README section with the test build build and run
instructions.

Author: bader

sycl/doc/GetStartedGuide.md

@@ -545,25 +545,9 @@ implementation conformance to Khronos\* SYCL\* specification. DPC++ compiler is
 expected to pass significant number of tests, and it keeps improving.
 
 Follow Khronos\* SYCL\* CTS instructions from
-[README](https://github.com/KhronosGroup/SYCL-CTS#sycl-121-conformance-test-suite)
+[README](https://github.com/KhronosGroup/SYCL-CTS#configuration--compilation)
 file to obtain test sources and instructions how build and execute the tests.
 
-To configure testing of DPC++ toochain set
-`SYCL_IMPLEMENTATION=Intel_SYCL` and
-`Intel_SYCL_ROOT=<path to the SYCL installation>` CMake variables.
-
-**Linux**:
-
-```bash
-cmake -DIntel_SYCL_ROOT=$DPCPP_HOME/deploy -DSYCL_IMPLEMENTATION=Intel_SYCL ...
-```
-
-**Windows (64-bit)**:
-
-```bat
-cmake -DIntel_SYCL_ROOT=%DPCPP_HOME%\deploy -DSYCL_IMPLEMENTATION=Intel_SYCL ...
-```
-
 ### Run simple DPC++ application
 
 A simple DPC++ or SYCL\* program consists of following parts: