Upgrade rust/crates/regex to 1.4.5

Test: make
Change-Id: I1d9343bd9712ddd57023af2c5d248993a2c31088
diff --git a/src/sparse.rs b/src/sparse.rs
index bc1b2b5..421d6b6 100644
--- a/src/sparse.rs
+++ b/src/sparse.rs
@@ -8,7 +8,7 @@
 /// entire set can also be done in constant time. Iteration yields elements
 /// in the order in which they were inserted.
 ///
-/// The data structure is based on: http://research.swtch.com/sparse
+/// The data structure is based on: https://research.swtch.com/sparse
 /// Note though that we don't actually use uninitialized memory. We generally
 /// reuse allocations, so the initial allocation cost is bareable. However,
 /// its other properties listed above are extremely useful.