Upgrade rust/crates/regex to 1.5.4

Test: make
Change-Id: I0eab39246dc2aea41a62c15661e350b490f06c1d
diff --git a/src/sparse.rs b/src/sparse.rs
index 421d6b6..98b7266 100644
--- a/src/sparse.rs
+++ b/src/sparse.rs
@@ -62,7 +62,7 @@
 }
 
 impl fmt::Debug for SparseSet {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "SparseSet({:?})", self.dense)
     }
 }