[BUGFIX] Fix displaying issue of buttons inside form fields

By setting the display property of buttons inside of input-groups to
"flex", the height of the element inside the button can be easier
controlled.

Resolves: #95451
Releases: master, 11.5
Change-Id: Ia41d6bf4421d8ad078509893c8b0177708767e5c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71459


Tested-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>

Build/Sources/Sass/typo3/_main_form.scss

@@ -601,3 +601,8 @@ $form-toggle-checked-bg-image: url("data:image/svg+xml, <svg xmlns='http://www.w
     // Consistent space between actions and listing
     margin: 0.5rem 0;
 }
+
+.input-group > .btn {
+    display: flex;
+    align-items: center;
+}