Remove test_date_empty_string function

Removed test for empty string handling in date command.

Author: sylvestre

tests/by-util/test_date.rs

@@ -860,17 +860,6 @@ fn test_date_military_timezone_j_variations() {
         .stdout_contains("UTC");
 }
 
-#[test]
-fn test_date_empty_string() {
-    // Empty string should be treated as midnight today
-    new_ucmd!()
-        .env("TZ", "UTC+1")
-        .arg("-d")
-        .arg("")
-        .succeeds()
-        .stdout_contains("00:00:00");
-}
-
 #[test]
 fn test_date_empty_string_variations() {
     // Test multiple variations of empty/whitespace strings