Revert of Update re2

third_party/re2/re2/testing/exhaustive2_test.cc

Index: third_party/re2/re2/testing/exhaustive2_test.cc
diff --git a/third_party/re2/re2/testing/exhaustive2_test.cc b/third_party/re2/re2/testing/exhaustive2_test.cc
index 6dc50166a6896eca05b4b4343675191560c00535..c5fec5b3e4a884b03a5717653864499fa7730bb2 100644
--- a/third_party/re2/re2/testing/exhaustive2_test.cc
+++ b/third_party/re2/re2/testing/exhaustive2_test.cc
@@ -23,7 +23,7 @@
 TEST(Punctuation, Literals) {
   vector<string> alphabet = Explode("()*+?{}[]\\^$.");
   vector<string> escaped = alphabet;
-  for (size_t i = 0; i < escaped.size(); i++)
+  for (int i = 0; i < escaped.size(); i++)
     escaped[i] = "\\" + escaped[i];
   ExhaustiveTest(1, 1, escaped, RegexpGenerator::EgrepOps(),
                  2, alphabet, "", "");