Upgrade rust/crates/regex to 1.4.2

Test: make
Change-Id: I29c3d9dd49dfbaac10af4048c1bdfabf4518bff4
diff --git a/Android.bp b/Android.bp
index f2e1727..ac83b2d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -36,6 +36,6 @@
 // dependent_library ["feature_list"]
 //   aho-corasick-0.7.14 "default,std"
 //   lazy_static-1.4.0
-//   memchr-2.3.3 "default,std,use_std"
-//   regex-syntax-0.6.20 "default,unicode,unicode-age,unicode-bool,unicode-case,unicode-gencat,unicode-perl,unicode-script,unicode-segment"
+//   memchr-2.3.4 "default,std,use_std"
+//   regex-syntax-0.6.21 "default,unicode,unicode-age,unicode-bool,unicode-case,unicode-gencat,unicode-perl,unicode-script,unicode-segment"
 //   thread_local-1.0.1