Update grafana/promtail Docker tag to v3

Signed-off-by: Marcus Noble <github@marcusnoble.co.uk>

manifests/nextcloud_chart/manifest.yaml

@@ -56,7 +56,9 @@ data:
   general.config.php: |-
     <?php
     $CONFIG = array (
-        'overwriteprotocol' => 'https'
+        'overwriteprotocol' => 'https',
+        'loglevel' => 1,
+        'log_rotate_size' => 100 * 1024 * 1024
     );
   .htaccess: |-
     # line below if for Apache 2.4