Remove googletest from the action cache

This solves the issues presented in madgraph5#1040, madgraph5#1045, madgraph5#1048, madgraph5#1051: apparently,
googletest is build once and then cached: if it had been built on an
Intel runner with AVX512 support, and the same is restored on an AMD
runner without AVX512, then the runTest.exe would fail with Illegal
Instruction.

Author: Qubitol

.github/workflows/testsuite_oneprocess.yml

@@ -230,7 +230,6 @@ jobs:
         path: |
           CCACHE_DIR
           DOWNLOADS
-          test/googletest
         key: buildcache-${{ runner.os }}-${{ inputs.process }}-${{ matrix.fptype }}-${{ steps.split.outputs.prnum }}-${{ github.run_id }}
         restore-keys: |
           buildcache-${{ runner.os }}-${{ inputs.process }}-${{ matrix.fptype }}-${{ steps.split.outputs.prnum }}