Rename the /database/procedure route to be unstable (#3723)

# Description of Changes

Title.

Closes #3644 .

# API and ABI breaking changes

Moves an unreleased HTTP route to make it explicitly unstable.

# Expected complexity level and risk

1

# Testing

<!-- Describe any testing you've done, and any testing you'd like your
reviewers to do,
so that you're confident that all the changes work as expected! -->

- [x] Used `curl` to hit the previous, not-unstable-looking route, got a
404.
- [x] Used `curl` to hit the new, obviously-unstable route, got a proper
response.

Author: gefjon

crates/client-api/src/routes/database.rs

@@ -1237,7 +1237,7 @@ where
             .route("/identity", self.identity_get)
             .route("/subscribe", self.subscribe_get)
             .route("/call/:reducer", self.call_reducer_post)
-            .route("/procedure/:procedure", self.call_procedure_post)
+            .route("/unstable/procedure/:procedure", self.call_procedure_post)
             .route("/schema", self.schema_get)
             .route("/logs", self.logs_get)
             .route("/sql", self.sql_post)