Update C/C++ Clang and GCC versions.rst

Author: AlonaHlobina

docs/codeql/support/reusables/versions-compilers.rst

@@ -4,9 +4,9 @@
    :stub-columns: 1
 
    Language,Variants,Compilers,Extensions
-   C/C++,"C89, C99, C11, C18, C++98, C++03, C++11, C++14, C++17","Clang (and clang-cl [1]_) extensions (up to Clang 9.0),
+   C/C++,"C89, C99, C11, C18, C++98, C++03, C++11, C++14, C++17","Clang (and clang-cl [1]_) extensions (up to Clang 12.0),
 
-   GNU extensions (up to GCC 9.2),
+   GNU extensions (up to GCC 9.4),
 
    Microsoft extensions (up to VS 2019),