Migrate soy templates off of calling deprecated isLast

Change-Id: I866e811bfcf3d53402656878d95a3b9bdb144b9d
diff --git a/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdated.soy b/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdated.soy
index cd57453..c570bd7 100644
--- a/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdated.soy
+++ b/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdated.soy
@@ -85,8 +85,8 @@
   {@param checkers: ?}
   {if length($checkers) > 0}
     {$state}:{sp}
-    {for $checker in $checkers}
-      {$checker.name}{if not isLast($checker)},{sp}{/if}
+    {for $checker, $index in $checkers}
+      {$checker.name}{if $index < length($checkers) - 1},{sp}{/if}
     {/for}
     {\n}
   {/if}
diff --git a/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdatedHtml.soy b/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdatedHtml.soy
index 0f35c40..13bfa8a 100644
--- a/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdatedHtml.soy
+++ b/resources/com/google/gerrit/plugins/checks/email/CombinedCheckStateUpdatedHtml.soy
@@ -103,13 +103,13 @@
   {@param checkers: ?}
   {if length($checkers) > 0}
     <strong>{$state}:</strong>{sp}
-    {for $checker in $checkers}
+    {for $checker, $index in $checkers}
       {if $checker.check.url}
         <a href="{$checker.check.url}">{$checker.name}</a>
       {else}
         {$checker.name}
       {/if}
-      {if not isLast($checker)},{sp}{/if}
+      {if $index < length($checkers) - 1},{sp}{/if}
     {/for}
     <br>
   {/if}