fix: update test crate rmcp version to 0.15.0 to match workspace patch

The integration test crate pinned rmcp to 0.14.0 while the workspace
patch targets 0.15.0, causing CI to use the unpatched crates.io version
which lacks the StoredCredentials::granted_scopes field and has
incompatible ServerHandler trait bounds.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>

Author: its-mash

Cargo.lock

@@ -50,7 +50,7 @@ url = "2.5"
 parking_lot = "0.12"
 
 # RMCP for streamable HTTP transport tests
-rmcp = { version = "0.14.0", features = [
+rmcp = { version = "0.15.0", features = [
     "client",
     "server",
     "transport-streamable-http-server",