chore: bump dafny verification version to 4.7

Author: ajewellamz

.github/workflows/ci_verification.yml

@@ -50,7 +50,7 @@ jobs:
         uses: dafny-lang/[email protected]
         with:
           # A && B || C is the closest thing to an if .. then ... else ... or ?: expression the GitHub Actions syntax supports.
-          dafny-version: ${{ (github.event_name == 'schedule' || inputs.nightly) && 'nightly-latest' || '4.6.0' }}
+          dafny-version: ${{ (github.event_name == 'schedule' || inputs.nightly) && 'nightly-latest' || '4.7.0' }}
 
       - name: Regenerate code using smithy-dafny if necessary
         if: ${{ github.event_name == 'schedule' || inputs.nightly }}