Add remove-all-unused-imports to autoflake invocation (#210)

* Added remove-all-unused-imports to autoflake invocation

* Update scripts/lint

Co-authored-by: Josep Cugat <jcugat@gmail.com>

Co-authored-by: Josep Cugat <jcugat@gmail.com>

Author: cdeler

scripts/lint

@@ -8,7 +8,7 @@ export SOURCE_FILES="httpcore tests"
 
 set -x
 
-${PREFIX}autoflake --in-place --recursive $SOURCE_FILES
+${PREFIX}autoflake --in-place --recursive --remove-all-unused-imports $SOURCE_FILES
 ${PREFIX}isort --project=httpcore $SOURCE_FILES
 ${PREFIX}black $SOURCE_FILES