Update logging_sample_config.md (#14868)

You do not have to restart synapse to reload the log config.

changelog.d/14868.doc

+Minor corrections to the logging configuration documentation.

docs/usage/configuration/logging_sample_config.md

 # Logging Sample Configuration File
 
 Below is a sample logging configuration file. This file can be tweaked to control how your
-homeserver will output logs. A restart of the server is generally required to apply any
-changes made to this file. The value of the `log_config` option in your homeserver
-config should be the path to this file.
+homeserver will output logs. The value of the `log_config` option in your homeserver config
+should be the path to this file.
+
+To apply changes made to this file, send Synapse a SIGHUP signal (or, if using `systemd`, run
+`systemctl reload` on the Synapse service).
 
 Note that a default logging configuration (shown below) is created automatically alongside
 the homeserver config when following the [installation instructions](../../setup/installation.md).