Revert new default form styles (#15100)

Closes #15071

This PR reverts the changes in #15036 which add consistent base styles
for buttons and form controls to Preflight.

While this felt like a good idea (for the reasons explained in that PR),
practically this is just too disruptive of a change for people upgrading
from v3 to v4.

While updating some of our projects to v4 we found ourselves adding
classes to undo styles more often than we expected, and it also felt
inconsistent to have to use a different set of classes to style a link
or a button when we wanted them to look the same.

We also decided it feels a little strange that you could change the
border color of an element without ever specifying that it should have a
border, for example this just feels a little wrong:

```html
<button class="border-blue-500">
```

We also needed to set a default `color-scheme` value for any of this
stuff to work which breaks the ability to use the `color-scheme` meta
tag.

Since this change was a fairly major breaking change and we aren't
feeling much benefit from it, it doesn't feel worth making this change
for v4.

---------

Co-authored-by: Philipp Spiess <hello@philippspiess.com>

Author: 2 people

CHANGELOG.md

@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Use configured `--letter-spacing` values for custom font size utilities ([#15099](https://github.com/tailwindlabs/tailwindcss/pull/15099))
 - Ensure `space-x/y-*` and `divide-x/y-*` with variants can undo `space-x/y-reverse` and `divide-x/y-reverse` ([#15094](https://github.com/tailwindlabs/tailwindcss/pull/15094))
 
+### Changed
+
+- Revert the new base styles for buttons and form controls ([#15100](https://github.com/tailwindlabs/tailwindcss/pull/15100))
+
 ## [4.0.0-beta.1] - 2024-11-21
 
 ### Added