Remove SHARED_GC job from compilers.yml

It's a duplicate of the one in ubuntu.yml

.github/workflows/compilers.yml

@@ -209,11 +209,6 @@ jobs:
           - { name: YJIT_FORCE_ENABLE,              env: { cppflags: '-DYJIT_FORCE_ENABLE' } }
 #         - { name: RJIT_FORCE_ENABLE,              env: { cppflags: '-DRJIT_FORCE_ENABLE' } }
           - { name: UNIVERSAL_PARSER,               env: { cppflags: '-DUNIVERSAL_PARSER' } }
-          - name: SHARED_GC
-            shared_gc: true
-            shared_gc_dir: '/ruby_gc'
-            env:
-              append_configure: '--with-shared-gc=/ruby_gc'
 
     name: ${{ matrix.entry.name }}
 
@@ -261,13 +256,6 @@ jobs:
           }}
           --${{ matrix.entry.shared || 'enable' }}-shared
 
-      - name: Build shared GC
-        run: >
-          echo "RUBY_GC_LIBRARY=librubygc.default.so" >> $GITHUB_ENV &&
-          mkdir ${{ matrix.entry.shared_gc_dir }} &&
-          make shared-gc SHARED_GC=default
-        if: ${{ matrix.entry.shared_gc }}
-
       - name: Add to ext/Setup
         id: ext-setup
         run: |