Fixed incompatibility with django_redis >= 4.12.0

Fixed bug caused by trying to use global level logger variable from django_redis.cache that has been moved to django_redis.cache.RedisCache instance attribute since django_redis 4.12.0 release.

Co-authored-by: rzelazo <62251572+rzelazo@users.noreply.github.com>

Author: ulgens

django_prometheus/cache/backends/redis.py

@@ -21,7 +21,7 @@ def get(self, key, default=None, version=None, client=None):
             django_cache_get_fail_total.labels(backend="redis").inc()
             if self._ignore_exceptions:
                 if self._log_ignored_exceptions:
-                    cache.logger.error(str(e))
+                    self.logger.error(str(e))
                 return default
             raise
         else: