Fix clippy issue alerting of elided lifetime (#194)

diff --git a/rust/ittapi/src/region.rs b/rust/ittapi/src/region.rs
index 9f027c5..5430d8a 100644
--- a/rust/ittapi/src/region.rs
+++ b/rust/ittapi/src/region.rs
@@ -48,7 +48,7 @@
     /// ```
     #[inline]
     #[must_use]
-    pub fn mark(&self) -> MarkedRegion {
+    pub fn mark(&self) -> MarkedRegion<'_> {
         unsafe { ittapi_sys::__itt_mark_pt_region_begin(self.0) };
         MarkedRegion(self)
     }