Remove unnecessary null checks for game client

Remove unnecessary null checks for game client from plugins, as now
client is always not null in all of them, since in the case of it being
null the plugins are not even started.

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

runelite-plugin-archetype/src/main/resources/archetype-resources/src/main/java/ExamplePlugin.java

@@ -27,7 +27,6 @@ public class ExamplePlugin extends Plugin
 	private static final Logger logger = LoggerFactory.getLogger(ExamplePlugin.class);
 
 	@Inject
-	@Nullable
 	Client client;
 
 	@Inject