[mod] make python code pylint 2.16.1 compliant

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/engines/crossref.py

@@ -2,6 +2,7 @@
 # lint: pylint
 """Semantic Scholar (Science)
 """
+# pylint: disable=use-dict-literal
 
 from urllib.parse import urlencode
 from searx.utils import html_to_text

searx/engines/docker_hub.py

@@ -3,6 +3,7 @@
 """Docker Hub (IT)
 
 """
+# pylint: disable=use-dict-literal
 
 from json import loads
 from urllib.parse import urlencode

searx/engines/gigablast.py

@@ -3,7 +3,7 @@
 """
  Gigablast (Web)
 """
-# pylint: disable=invalid-name
+# pylint: disable=invalid-name, use-dict-literal
 
 import re
 from time import time