Revert "Add job to test racket CGC on Linux and macOS (#2918)"

This reverts commit 568433c1a9.

There are some flaky tests that need to be fixed. See differences between:
    - https://github.com/racket/racket/runs/321618267
    - https://github.com/racket/racket/runs/321344052

.github/workflows/ci-push.yml

@@ -190,36 +190,3 @@ jobs:
         name: racketcs-${{ matrix.os }}-x64_git${{ github.sha }}
         path: ../racketcs-${{ matrix.os }}-x64_git${{ github.sha }}.tar.bz2
 
-# Tests
-  test-cgc:
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-18.04, macos-latest]
-        cify: [cify, nocify]
-
-    runs-on: ${{ matrix.os }}
-
-    needs: build-racketcgc
-
-    steps:
-      - uses: actions/checkout@v1
-      - uses: actions/download-artifact@master
-        with:
-          name: racketcgc-${{ matrix.os }}-${{ matrix.cify }}-x64_git${{ github.sha }}
-          path: ../
-      - name: Untar
-        working-directory: ../
-        run: tar -xvjf racketcgc-${{ matrix.os }}-${{ matrix.cify }}-x64_git${{ github.sha }}.tar.bz2
-      - name: Extend PATH with Racket executable
-        working-directory: ../
-        run: echo "::set-env name=PATH::$PWD/racketcgc/bin:$PATH"
-      - name: Check for Racket
-        run: racket --version
-      - name: Install catalog and required packages
-        run: |
-          racket -l- pkg/dirs-catalog --immediate $PWD/rktcat $PWD/pkgs/
-          raco pkg config --set catalogs $PWD/rktcat/ https://pkgs.racket-lang.org https://planet-compats.racket-lang.org
-          raco pkg install --auto racket-test
-      - name: Run test
-        run: raco test -l tests/racket/test