[mod] engines: remove uses of enable_http2 = False

This has only been needed because we were flagged by HTTP2 fingerprinting.
Now, since we use curl cffi, we can bypass the fingerpinting, so we can
use HTTP2 just fine without getting blocked.

searx/engines/pexels.py

@@ -8,7 +8,7 @@ from urllib.parse import urlencode
 from lxml import html
 
 from searx.result_types import EngineResults
-from searx.utils import eval_xpath_list, gen_useragent
+from searx.utils import eval_xpath_list
 from searx.enginelib import EngineCache
 from searx.exceptions import SearxEngineAPIException, SearxEngineAccessDeniedException
 from searx.network import get
@@ -44,8 +44,6 @@ SECRET_KEY_DB_KEY = "secret-key"
 CACHE: EngineCache
 """Cache to store the secret API key for the engine."""
 
-enable_http2 = False
-
 
 def setup(engine_settings: dict[str, t.Any]) -> bool:
     global CACHE  # pylint: disable=global-statement
@@ -56,13 +54,7 @@ def setup(engine_settings: dict[str, t.Any]) -> bool:
 def _get_secret_key():
     resp = get(
         base_url,
-        headers={
-            # circumvents Cloudflare bot protections
-            "User-Agent": gen_useragent(),
-            "Referer": base_url,
-            "Sec-GPC": "1",
-            "Connection": "keep-alive",
-        },
+        headers={"Referer": base_url},
     )
 
     if resp.status_code != 200:
@@ -105,8 +97,6 @@ def request(query, params):
 
     params["headers"]["secret-key"] = secret_key
 
-    return params
-
 
 def response(resp):
     res = EngineResults()