General: Improve search input alignment on mobile.

Remove an end margin misalignment on the search input for posts, comments, themes, and plugins. 

Props ronak44, sourav08, dilipbheda, SirLouen, nikunj8866, darshitrajyaguru97, rollybueno, shailu25, sabernhardt, joedolson.
Fixes #63310.

git-svn-id: https://develop.svn.wordpress.org/trunk@60975 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-admin/css/forms.css

@@ -727,7 +727,6 @@ p.search-box {
 	clear: left;
 }
 
-.search-box input[name="s"],
 .tablenav .search-plugins input[name="s"],
 .tagsdiv .newtag {
 	float: left;
@@ -1653,11 +1652,15 @@ table.form-table td .updated p {
 	}
 
 	p.search-box input[name="s"] {
-		float: none;
 		width: 100%;
+		float: none;
 		margin-bottom: 10px;
 		vertical-align: middle;
 	}
+	.js.plugins-php .search-box .wp-filter-search {
+		width: 100%;
+		margin-bottom: 0;
+	}
 
 	p.search-box input[type="submit"] {
 		margin-bottom: 10px;

src/wp-admin/css/themes.css

@@ -961,12 +961,7 @@ body.folded .theme-browser ~ .theme-overlay .theme-wrap {
 	}
 
 	.themes-php .wp-filter-search {
-		float: none;
-		clear: both;
-		left: 0;
-		right: 0;
 		width: 100%;
-		max-width: 280px;
 	}
 
 	.theme-install-php .wp-filter p.search-box {