Update deployment/signals.md

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Co-authored-by: Shizuo Fujita <watson1978@gmail.com>

Author: daipom

deployment/signals.md

@@ -62,7 +62,7 @@ Reloads the configuration file by gracefully re-constructing the data pipeline.
 Limitations:
 
 * A change to System Configuration (`<system>`) is ignored.
-* All plugins must not use class variable when restarting.
+* All plugins must not use class variable.
 
 ### SIGHUP