Upload: Improve file input and button alignment in plugin/theme upload form.

Resets flexbox on smaller screens. Improves vertical alignment on large screens.
Follow-up to [47599] and [47271].

Props mukesh27, DarkoG.
See #48859, #49914.
Fixes #49951.

Built from https://develop.svn.wordpress.org/trunk@47750


git-svn-id: http://core.svn.wordpress.org/trunk@47526 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/themes.css

@@ -896,7 +896,7 @@ body.folded .theme-browser ~ .theme-overlay .theme-wrap {
 	.theme-browser .theme:nth-child(3n) {
 		margin-right: 0;
 	}
-	
+
 	.theme-overlay .theme-about {
 		bottom: 105px;
 	}
@@ -1060,6 +1060,7 @@ body.folded .theme-browser ~ .theme-overlay .theme-wrap {
 	max-width: 380px;
 	display: flex;
 	justify-content: space-between;
+	align-items: center;
 }
 
 .upload-theme .install-help,
@@ -1918,6 +1919,11 @@ body.full-overlay-active {
 		padding-top: 4px;
 		padding-bottom: 4px;
 	}
+
+	.upload-theme .wp-upload-form,
+	.upload-plugin .wp-upload-form {
+		display: block;
+	}
 }
 
 @media aural {