Remove version param from get_lsn_by_timestamp (#6551)

This removes the last remnants of the version param added by #5608 ,
concluding the transition plan laid out in
https://github.com/neondatabase/cloud/pull/7553#discussion_r1370473911 .
It follows PR https://github.com/neondatabase/cloud/pull/9202, which we
now assume has been deployed to all environments.

Full history:

* https://github.com/neondatabase/neon/pull/5608 
* https://github.com/neondatabase/cloud/pull/7553
* https://github.com/neondatabase/neon/pull/6178
* https://github.com/neondatabase/cloud/pull/9202

pageserver/src/http/openapi_spec.yml

@@ -419,12 +419,6 @@ paths:
             type: string
             format: date-time
           description: A timestamp to get the LSN
-        - name: version
-          in: query
-          required: false
-          schema:
-            type: integer
-          description: The version of the endpoint to use
       responses:
         "200":
           description: OK

test_runner/fixtures/pageserver/http.py

@@ -549,17 +549,12 @@ class PageserverHttpClient(requests.Session):
         tenant_id: Union[TenantId, TenantShardId],
         timeline_id: TimelineId,
         timestamp,
-        version: Optional[int] = None,
     ):
         log.info(
             f"Requesting lsn by timestamp {timestamp}, tenant {tenant_id}, timeline {timeline_id}"
         )
-        if version is None:
-            version_str = ""
-        else:
-            version_str = f"&version={version}"
         res = self.get(
-            f"http://localhost:{self.port}/v1/tenant/{tenant_id}/timeline/{timeline_id}/get_lsn_by_timestamp?timestamp={timestamp}{version_str}",
+            f"http://localhost:{self.port}/v1/tenant/{tenant_id}/timeline/{timeline_id}/get_lsn_by_timestamp?timestamp={timestamp}",
         )
         self.verbose_error(res)
         res_json = res.json()

test_runner/regress/test_lsn_mapping.py

@@ -109,7 +109,7 @@ def test_lsn_mapping(neon_env_builder: NeonEnvBuilder):
         # Timestamp is in the unreachable past
         probe_timestamp = tbl[0][1] - timedelta(hours=10)
         result = client.timeline_get_lsn_by_timestamp(
-            tenant_id, timeline_id_child, f"{probe_timestamp.isoformat()}Z", 2
+            tenant_id, timeline_id_child, f"{probe_timestamp.isoformat()}Z"
         )
         assert result["kind"] == "past"
         # make sure that we return the minimum lsn here at the start of the range