Fix various typos in ART's comments and string literals.

Change-Id: I85d628055b1a61647a77fef730c9631c234e22a2
diff --git a/runtime/utf_test.cc b/runtime/utf_test.cc
index 5239e40..c67879b 100644
--- a/runtime/utf_test.cc
+++ b/runtime/utf_test.cc
@@ -353,7 +353,7 @@
     if (codePoint <= 0xffff) {
       if (codePoint >= 0xd800 && codePoint <= 0xdfff) {
         // According to the Unicode standard, no character will ever
-        // be assigned to these code points, and they can not be encoded
+        // be assigned to these code points, and they cannot be encoded
         // into either utf-16 or utf-8.
         continue;
       }