ci: fix draft conformance version env var in client step

Author: DaleSeo

.github/workflows/conformance.yml

@@ -157,7 +157,7 @@ jobs:
       # SEP-2322 MRTR client scenario (spec 2026-07-28).
       - name: Run SEP-2322 MRTR client scenario
         run: |
-          npx -y "@modelcontextprotocol/conformance@${CONFORMANCE_DRAFT_VERSION}" client \
+          npx -y "@modelcontextprotocol/conformance@${DRAFT_CONFORMANCE_VERSION}" client \
             --command "$(pwd)/target/debug/conformance-client" \
             --scenario sep-2322-client-request-state \
             -o conformance-client-results/mrtr