Remove C++ workflow run from image suite PR

Author: treeform

.github/workflows/build.yml

@@ -24,5 +24,4 @@ jobs:
           cd ..
           nimby install -g pixie/pixie.nimble
       - run: nim r tests/tests.nim
-      - run: nim cpp -r tests/tests.nim
       - run: nim r tests/imagetestsuite.nim