chore: unset tz env in test (#6984)

chore/unset-tz-env-in-test:
 ### Commit Message

 Add environment variable cleanup in timezone tests

 - Updated `timezone.rs` to include removal of the `TZ` environment variable in the `test_from_tz_string` function to ensure a clean test environment.

Signed-off-by: Lei, HUANG <mrsatangel@gmail.com>

src/common/time/src/timezone.rs

@@ -173,6 +173,9 @@ mod tests {
 
     #[test]
     fn test_from_tz_string() {
+        unsafe {
+            std::env::remove_var("TZ");
+        }
         assert_eq!(
             Timezone::Named(Tz::UTC),
             Timezone::from_tz_string("SYSTEM").unwrap()