fix: remove deprecated create_realtime_partition function and update test references

- Deleted the create_realtime_partition SQL function and related comments
- Updated test scripts to no longer call create_realtime_partition
- Replaced pgflow.read_with_poll with pgmq.read_with_poll in client code
- Ensured tests focus on existing functionality without partition creation
- Minor adjustments to test setup for consistency and clarity

Author: jumski

.changeset/pgmq-version-bump.md

@@ -0,0 +1,10 @@
+---
+'@pgflow/core': minor
+'@pgflow/edge-worker': minor
+---
+
+BREAKING CHANGE: This version requires pgmq 1.5.0 or higher and will NOT work with pgmq 1.4.x.
+
+The code now depends on schema changes introduced in pgmq 1.5.0 (specifically the headers column in message_record type). The compatibility layer that allowed pgflow to work with pgmq 1.4.x has been removed.
+
+If you are using Supabase, pgmq 1.5.0+ is included by default in recent versions. If you are self-hosting, you must upgrade pgmq to version 1.5.0 or higher before upgrading pgflow.