[forms] Remove tip for skipping validation group section
Update installation.rst

typo in cookbook/bundle/installation
Merge pull request #2981 from bicpi/remove_tip_for_validation_groups

[forms] Remove tip for skipping validation group section
Merge branch '2.0' into 2.1
Merge branch '2.1' into 2.2
Merge pull request #2984 from peterkokot/2.1

Update installation.rst
Merge branch '2.1' into 2.2
clarifies that resolve() does return a plain array of options