Remove custom valgrind suppressions

cargo-valgrind now ships with a default suppression list.

Author: purplesyringa

.github/workflows/ci.yml

@@ -366,8 +366,6 @@ jobs:
   valgrind:
     timeout-minutes: 5
     runs-on: ubuntu-latest
-    env:
-      VALGRINDFLAGS: --suppressions=valgrind.supp
     if: success() || failure()
     steps:
       - name: Checkout