Fix invalid HTML in "should allow html entities" tooltip unit test

Refs #14090.
Also, fix one typo.
Merge pull request #14091 from twbs/tooltip-test-html-fix

Fix unusual HTML in "should allow html entities" tooltip unit test
Fix IE8 reporting height style as all uppercase
Fix IE8 reporting type object for `getBoundingClientRect`
`document.head` is undefined in IE8
Merge pull request #14090 from hnrch02/unit-tests-ie8

Fix IE8 problems with unit tests
Update uglify-js to v2.4.14.
Run `grunt`.
Update dependencies.
Update uglify-js to v2.4.15.
Run `grunt`.
Fix text on ".progress-bar .sr-only" elements.
Merge pull request #14112 from vsn4ik/fix-sr-only-progress-bars

Fix text on ".progress-bar .sr-only" elements in docs
dropdowns.html: Add role="button" and id="..." to link in example.
Merge pull request #14113 from vsn4ik/add-attributes-for-dropdown-example

dropdowns.html: Add role="button" and id="..." to link in example.