DNR: Remove stale TODO.

Remove a stale TODO from declarativeNetRequest code. This was fixed in
https://chromium-review.googlesource.com/c/chromium/src/+/2016201.

BUG=974391
TBR=lazyboy@chromium.org

Change-Id: I374b08f428491cdd678c334238de8d5d3d23aba3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2092873Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747957}

extensions/browser/api/declarative_net_request/indexed_rule.cc

@@ -467,8 +467,6 @@ ParseResult IndexedRule::CreateIndexedRule(dnr_api::Rule parsed_rule,
   if (parsed_rule.condition.url_filter && parsed_rule.condition.regex_filter)
     return ParseResult::ERROR_MULTIPLE_FILTERS_SPECIFIED;
 
-  // TODO(crbug.com/974391): Implement limits on the number of regex rules an
-  // extension can specify.
   const bool is_regex_rule = !!parsed_rule.condition.regex_filter;
 
   if (!is_regex_rule && indexed_rule->regex_substitution)