fix syntax

Author: hendrikmuhs

.github/workflows/keyvi.yml

@@ -83,7 +83,7 @@ jobs:
         if: matrix.type == 'Coverage'
         env:
           COVERALLS_REPO_TOKEN: ${{ secrets.COVERALLS_REPO_TOKEN }}
-          COVERALLS_PARALLEL=true
+          COVERALLS_PARALLEL: true
         run: |
           python -m pip install git+https://github.com/hendrikmuhs/cpp-coveralls.git@gcov-template-coverage --user
           export PATH="/home/runner/.local/bin:$PATH"