Remove C++03,11,2a from GHA

Author: jeremy-murphy

.github/workflows/ci.yml

@@ -47,10 +47,10 @@ jobs:
         run: 'echo "using $TOOLSET : : ${{ matrix.compiler }} ;" > ~/user-config.jam && echo "using mpi ;" >> ~/user-config.jam'
         working-directory: ../boost-root
       - name: Config info
-        run: ../../../b2 print_config_info toolset=$TOOLSET cxxstd=03,11,14,17,2a
+        run: ../../../b2 print_config_info toolset=$TOOLSET cxxstd=14,17,20
         working-directory: ../boost-root/libs/config/test
       - name: Test
-        run: ../../../b2 toolset=$TOOLSET cxxstd=03,11,14,17,2a
+        run: ../../../b2 toolset=$TOOLSET cxxstd=14,17,20
         working-directory: ../boost-root/libs/graph_parallel/test
   macos:
     runs-on: macos-latest
@@ -89,8 +89,8 @@ jobs:
       - name: Generate user-config
         run: echo "using mpi ;" > ~/user-config.jam
       - name: Config info
-        run: ../../../b2 print_config_info toolset=${{ matrix.toolset }} cxxstd=03,11,14,17,2a
+        run: ../../../b2 print_config_info toolset=${{ matrix.toolset }} cxxstd=14,17,20
         working-directory: ../boost-root/libs/config/test
       - name: Test
-        run: ../../../b2 toolset=${{ matrix.toolset }} cxxstd=03,11,14,17,2a define=CI_SUPPRESS_KNOWN_ISSUES
+        run: ../../../b2 toolset=${{ matrix.toolset }} cxxstd=14,17,20 define=CI_SUPPRESS_KNOWN_ISSUES
         working-directory: ../boost-root/libs/graph_parallel/test