github: c++11 is no longer supported by GTest in CI

Author: davvid

.github/workflows/build.yml

@@ -11,7 +11,7 @@ jobs:
       matrix:
         os: [ubuntu]
         config: [Debug, Release]
-        standard: [c++11, c++14, c++17, c++20]
+        standard: [c++14, c++17, c++20]
     name: ${{matrix.os}}-${{matrix.config}}-${{matrix.standard}}
     runs-on: ${{matrix.os}}-latest