Update grid-framework.less

The `when (@index = 1)` guards are not needed cause the mixins already only match on arity.
Fix #14936: Use correct left/right and margin on tooltip arrows
Add #14868 to the compatibility docs
Use Jekyll data for Wall of Browser Bugs
Remove duplicate code from Customizer/Gruntfile by sharing it
Merge pull request #14982 from twbs/grunt-customizer-share-common

Remove duplicate code from Customizer/Gruntfile by sharing it
Use autoprefixer for Customizer builds
Merge pull request #14980 from twbs/customizer-autoprefixer

Use autoprefixer for Customizer builds
Merge pull request #14987 from twbs/overengineer-wall-of-browser-bugs

Use Jekyll data for Wall of Browser Bugs
HTTPS for Apple Safari Radar in bugify filter
Add initialization examples to tooltip and popover "Opt-in functionality" callouts

Fixes #14950.
Closes #15015 by merging it.
Fix modal backdrop overlaying the modal's scrollbar

Fixes #14916.
Merge pull request #14938 from twbs/oh_arrow_where_art_thou

Fix #14936: Use correct left/right and margin on tooltip arrows
Deprecate diagonal tooltip classes
Merge pull request #14927 from twbs/fix-modal-backdrop-above-scrollbar

Fix modal backdrop overlaying the modal's scrollbar
Merge pull request #15019 from twbs/whoomp_there_it_was

Deprecate diagonal tooltip classes
grunt
Update head of all visual tests to use our basic template
Have Carousel ignore keyboard events from <input>s or <textarea>s; fixes #14991
Center modal dialog at all times