Remove striped tables in UI (#36509)

We've been cutting down on the "striped" tables (where rows are using
alternate row background colors). This completely removes them as I
think such a design looks outdated.

The removal of selectors starting with `.ui[class*="very
basic"].table:not(.striped)` is needed because of a specificity issue in
the CSS where table cells would otherwise render with incorrect padding.

Example of one affected table:

<img width="1027" height="224" alt="image"
src="https://github.com/user-attachments/assets/2f3006ca-99a1-4655-afdb-b7cd9e5f19c7"
/>

templates/repo/branch/list.tmpl

@@ -15,7 +15,7 @@
 			</h4>
 
 			<div class="ui attached table segment">
-				<table class="ui very basic striped fixed table single line">
+				<table class="ui very basic fixed table single line">
 					<tbody>
 						<tr>
 							<td>
@@ -83,7 +83,7 @@
 		</div>
 
 		<div class="ui attached table segment">
-			<table class="ui very basic striped fixed table single line">
+			<table class="ui very basic fixed table single line">
 				<tbody>
 					{{range .Branches}}
 						<tr>

templates/repo/commits_list.tmpl

@@ -1,5 +1,5 @@
 <div class="ui attached table segment commit-table">
-	<table class="ui very basic striped table unstackable" id="commits-table">
+	<table class="ui very basic table unstackable" id="commits-table">
 		<thead>
 			<tr>
 				<th class="three wide">{{ctx.Locale.Tr "repo.commits.author"}}</th>