[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/pixabay.py

@@ -27,9 +27,6 @@ time_range_support = True
 safesearch_map = {0: 'off', 1: '1', 2: '1'}
 time_range_map = {'day': '1d', 'week': '1w', 'month': '1m', 'year': '1y'}
 
-# using http2 returns forbidden errors
-enable_http2 = False
-
 
 def request(query, params):
     args = {
@@ -50,8 +47,6 @@ def request(query, params):
     # prevent automatic redirects to first page on pagination
     params['allow_redirects'] = False
 
-    return params
-
 
 def _image_result(result):
     return {