css: clean up css reset stylesheet.

Remove all unnecessary rules from our CSS reset stylesheet.

Our CSS reset was based on a combination of Eric Meyer's CSS reset [1]
and Nicholas Gallagher's normalize.css [2]. Neither had been updated in
over 10 years, so they both contained a lot of unnecessary cruft. This
included workarounds for bugs in ancient versions of IE, and rules for
elements we don't use. Some of these rules had already been removed
upstream, but we never synchronized our copy of normalize.css with it.

This fixes some minor issues with vertical alignment of form inputs,
caused by unnecessary `vertical-align: middle` rules.

[1]: https://meyerweb.com/eric/tools/css/reset/
[2]: https://nicolasgallagher.com/about-normalize-css/

app/javascript/src/styles/common/simple_form.scss

@@ -19,7 +19,6 @@ form.simple_form {
     label {
       display: inline;
       font-weight: normal;
-      vertical-align: middle;
     }
 
     input {