tests: remove ignored fair field (#11521)

Pageserver has been ignoring field
`tenant_config.timeline_get_throttle.fair`
for many monhts, since we removed it from the config struct in
neondatabase/neon#8539.

Refs
- epic https://github.com/neondatabase/cloud/issues/27320

test_runner/regress/test_pageserver_getpage_throttle.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import copy
 import json
 import uuid
 from typing import TYPE_CHECKING
@@ -44,7 +43,6 @@ def test_pageserver_getpage_throttle(neon_env_builder: NeonEnvBuilder, pg_bin: P
                 "refill_interval": "100ms",
                 "refill_amount": int(rate_limit_rps / 10),
                 "max": int(rate_limit_rps / 10),
-                "fair": True,
             },
         },
     )
@@ -139,63 +137,3 @@ def test_pageserver_getpage_throttle(neon_env_builder: NeonEnvBuilder, pg_bin: P
     assert pytest.approx(actual_throttled_secs + actual_smgr_query_seconds, 0.1) == duration_secs, (
         "most of the time in this test is spent throttled because the rate-limit's contribution to latency dominates"
     )
-
-
-throttle_config_with_field_fair_set = {
-    "task_kinds": ["PageRequestHandler"],
-    "fair": True,
-    "initial": 27,
-    "refill_interval": "43s",
-    "refill_amount": 23,
-    "max": 42,
-}
-
-
-def assert_throttle_config_with_field_fair_set(conf):
-    """
-    Field `fair` is ignored, so, responses don't contain it
-    """
-    without_fair = copy.deepcopy(throttle_config_with_field_fair_set)
-    without_fair.pop("fair")
-
-    assert conf == without_fair
-
-
-def test_throttle_fair_config_is_settable_but_ignored_in_mgmt_api(neon_env_builder: NeonEnvBuilder):
-    """
-    To be removed after https://github.com/neondatabase/neon/pull/8539 is rolled out.
-    """
-    env = neon_env_builder.init_start()
-    vps_http = env.storage_controller.pageserver_api()
-    # with_fair config should still be settable
-    vps_http.set_tenant_config(
-        env.initial_tenant,
-        {"timeline_get_throttle": throttle_config_with_field_fair_set},
-    )
-    conf = vps_http.tenant_config(env.initial_tenant)
-    assert_throttle_config_with_field_fair_set(conf.effective_config["timeline_get_throttle"])
-    assert_throttle_config_with_field_fair_set(
-        conf.tenant_specific_overrides["timeline_get_throttle"]
-    )
-
-
-def test_throttle_fair_config_is_settable_but_ignored_in_config_toml(
-    neon_env_builder: NeonEnvBuilder,
-):
-    """
-    To be removed after https://github.com/neondatabase/neon/pull/8539 is rolled out.
-    """
-
-    def set_tenant_config(ps_cfg):
-        tenant_config = ps_cfg.setdefault("tenant_config", {})
-        tenant_config["timeline_get_throttle"] = throttle_config_with_field_fair_set
-
-    neon_env_builder.pageserver_config_override = set_tenant_config
-    env = neon_env_builder.init_start()
-    ps_http = env.pageserver.http_client()
-    conf = ps_http.tenant_config(env.initial_tenant)
-    assert_throttle_config_with_field_fair_set(conf.effective_config["timeline_get_throttle"])
-
-    env.pageserver.allowed_errors.append(
-        r'.*ignoring unknown configuration item path="tenant_config\.timeline_get_throttle\.fair"*'
-    )