tests: Remove redundant log lines when starting an endpoint (#9316)

The "Starting postgres endpoint <name>" message is not needed, because
the neon_cli.py prints the neon_local command line used to start the
endpoint. That contains the same information. The "Postgres startup took
XX seconds" message is not very useful because no one pays attention to
those in the python test logs when things are going smoothly, and if you
do wonder about the startup speed, the same information and more can be
found in the compute log.

Before:

    2024-10-07 22:32:27.794 INFO [neon_fixtures.py:3492] Starting postgres endpoint ep-1
    2024-10-07 22:32:27.794 INFO [neon_cli.py:73] Running command "/tmp/neon/bin/neon_local endpoint start --safekeepers 1 ep-1"
    2024-10-07 22:32:27.901 INFO [neon_fixtures.py:3690] Postgres startup took 0.11398935317993164 seconds

After:

    2024-10-07 22:32:27.794 INFO [neon_cli.py:73] Running command "/tmp/neon/bin/neon_local endpoint start --safekeepers 1 ep-1"

test_runner/fixtures/neon_fixtures.py

@@ -3485,8 +3485,6 @@ def start(
         if safekeepers is not None:
             self.active_safekeepers = safekeepers
 
-        log.info(f"Starting postgres endpoint {self.endpoint_id}")
-
         self.env.neon_cli.endpoint_start(
             self.endpoint_id,
             safekeepers=self.active_safekeepers,
@@ -3666,8 +3664,6 @@ def create_start(
         Returns self.
         """
 
-        started_at = time.time()
-
         self.create(
             branch_name=branch_name,
             endpoint_id=endpoint_id,
@@ -3683,8 +3679,6 @@ def create_start(
             basebackup_request_tries=basebackup_request_tries,
         )
 
-        log.info(f"Postgres startup took {time.time() - started_at} seconds")
-
         return self
 
     def __enter__(self) -> Endpoint: