chore: use immutable semver tag v1.4.0

Author: SamMorrowDrums

.github/workflows/conformance.yml

@@ -17,7 +17,7 @@ jobs:
           fetch-depth: 0
 
       - name: Run MCP Conformance Test
-        uses: SamMorrowDrums/mcp-conformance-action@e431538d426a6668adbb5bd8f79798bbee192200 # v1
+        uses: SamMorrowDrums/mcp-conformance-action@e431538d426a6668adbb5bd8f79798bbee192200 # v1.4.0
         with:
           setup_go: "true"
           install_command: go mod download