Remove Stage/Unstage column headers from staging tables

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/resources/templates/changes.html

@@ -10,7 +10,7 @@
 <form method="post" th:action="@{/repo/{name}/stage(name=${name})}" th:if="${!#lists.isEmpty(modifiedFiles)}">
 <table border="1" cellpadding="4" cellspacing="0">
 <tr>
-<th>Stage</th>
+<th></th>
 <th>File</th>
 </tr>
 <tr th:each="file : ${modifiedFiles}">
@@ -27,7 +27,7 @@
 <form method="post" th:action="@{/repo/{name}/unstage(name=${name})}" th:if="${!#lists.isEmpty(stagedFiles)}">
 <table border="1" cellpadding="4" cellspacing="0">
 <tr>
-<th>Unstage</th>
+<th></th>
 <th>File</th>
 </tr>
 <tr th:each="file : ${stagedFiles}">