test_pageserver_max_throughput_getpage_at_latest_lsn: disable on CI (#6785)

## Problem
`test_pageserver_max_throughput_getpage_at_latest_lsn` is flaky which
makes CI status red pretty frequently. `benchmarks` is not a blocking
job (doesn't block `deploy`), so having it red might hide failures in
other jobs

Ref: https://github.com/neondatabase/neon/issues/6724

## Summary of changes
- Disable `test_pageserver_max_throughput_getpage_at_latest_lsn` on CI
until it fixed

test_runner/performance/pageserver/pagebench/test_pageserver_max_throughput_getpage_at_latest_lsn.py

@@ -1,4 +1,5 @@
 import json
+import os
 from pathlib import Path
 from typing import Any, Dict, Tuple
 
@@ -33,6 +34,10 @@ from performance.pageserver.util import ensure_pageserver_ready_for_benchmarking
 @pytest.mark.timeout(
     10000
 )  # TODO: this value is just "a really high number"; have this per instance type
+@pytest.mark.skipif(
+    os.getenv("CI", "false") == "true",
+    reason="The test if flaky on CI: https://github.com/neondatabase/neon/issues/6724",
+)
 def test_pageserver_max_throughput_getpage_at_latest_lsn(
     neon_env_builder: NeonEnvBuilder,
     zenbenchmark: NeonBenchmarker,