deps: downgrade to urllib3 v1 because v2 is not supported on Python 3.6 (#318)

Author: Anthirian

elkserver/docker/redelk-base/redelkinstalldata/scripts/requirements.txt

@@ -4,4 +4,4 @@ json2html==1.3.0
 pymsteams==0.1.14
 python-dateutil==2.8.2
 slack_sdk==3.13.0
-urllib3==2.5.0
+urllib3==1.26.20