GitHub: don't fail CI if coverage upload fails

See lightningnetwork/lnd#9508.

Author: guggero

.github/workflows/main.yaml

@@ -232,6 +232,7 @@ jobs:
       - name: Send coverage
         uses: shogo82148/actions-goveralls@v1
         if: matrix.unit_type == 'unit-cover'
+        continue-on-error: true
         with:
           path-to-profile: coverage.txt
           flag-name: 'unit'
@@ -347,5 +348,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: shogo82148/actions-goveralls@v1
+        continue-on-error: true
         with:
           parallel-finished: true