Upgrade rust/crates/regex to 1.4.5

Test: make
Change-Id: I1d9343bd9712ddd57023af2c5d248993a2c31088
diff --git a/src/expand.rs b/src/expand.rs
index fd2ab03..70dbf91 100644
--- a/src/expand.rs
+++ b/src/expand.rs
@@ -144,7 +144,8 @@
     }
     // We just verified that the range 0..cap_end is valid ASCII, so it must
     // therefore be valid UTF-8. If we really cared, we could avoid this UTF-8
-    // check with either unsafe or by parsing the number straight from &[u8].
+    // check via an unchecked conversion or by parsing the number straight from
+    // &[u8].
     let cap =
         str::from_utf8(&rep[i..cap_end]).expect("valid UTF-8 capture name");
     Some(CaptureRef {