Use tag when resolving keep-core contracts

We tag the latest `@keep-network/keep-core` package containing contracts
migrated on some environment with tag that is a name of that
environment. We can use that tag instead of the explicit version when
resolving contracts of dependant projects.

Author: michalinacienciala

.github/workflows/contracts.yaml

@@ -114,7 +114,7 @@ jobs:
         run: yarn install --frozen-lockfile
 
       - name: Resolve latest contracts
-        run: yarn upgrade @keep-network/keep-core@1.8.1-goerli.0
+        run: yarn upgrade @keep-network/keep-core@${{ github.event.inputs.environment }}
 
       - name: Configure tenderly
         env: