[sql] Fix typo in error message.

CL https://codereview.chromium.org/1419573008 fixed a typo, but made a
typo.

BUG=none
[email protected]

Review URL: https://codereview.chromium.org/1428523007

Cr-Commit-Position: refs/heads/master@{#358673}
diff --git a/sql/connection.cc b/sql/connection.cc
index 2bfad2db..185b9551 100644
--- a/sql/connection.cc
+++ b/sql/connection.cc
@@ -1285,7 +1285,7 @@
 
 bool Connection::CommitTransaction() {
   if (!transaction_nesting_) {
-    DLOG_IF(FATAL, !poisoned_) << "Committing back a nonexistent transaction";
+    DLOG_IF(FATAL, !poisoned_) << "Committing a nonexistent transaction";
     return false;
   }
   transaction_nesting_--;