fix indentation in read me

Author: ziming

README.md

@@ -33,8 +33,8 @@ use Ziming\LaravelMemoryHealthCheck\UsedMemoryCheck;
 
 Health::checks([
     UsedMemoryCheck::new()
-    ->warnWhenUsedSpaceIsAbovePercentage(70)
-    ->failWhenUsedSpaceIsAbovePercentage(90),
+        ->warnWhenUsedSpaceIsAbovePercentage(70)
+        ->failWhenUsedSpaceIsAbovePercentage(90),
 ]);
 ```