[JinJa2] Corrected the macro used for comments on the test file. (#3373)

* Corrected the macro for comments on the test file.
* Added current_date (utcnow()) variable available for template macros.
* Removed unnecessary datetime import from macros file.
* Regenerated all practice exercise test files to add timestamp.
* Changed `datetime.now(tz=timezone.utc)` to `datetime.now(tz=timezone.utc).date()`
* Second regeneration to remove `timestamp` and just keep `date` for test files.
[no important files changed]

exercises/practice/reverse-string/reverse_string_test.py

@@ -4,7 +4,9 @@ from reverse_string import (
     reverse,
 )
 
-# Tests adapted from `problem-specifications//canonical-data.json`
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/reverse-string/canonical-data.json
+# File last updated on 2023-07-14
 
 
 class ReverseStringTest(unittest.TestCase):