Fix typo in SECURITY.md [skip ci]

Author: machour

.github/SECURITY.md

@@ -3,4 +3,4 @@
 Please use the [security issue form](https://www.yiiframework.com/security) to report to us any security issue you find in Yii.
 DO NOT use the issue tracker or discuss it in the public forum as it will cause more damage than help.
 
-Please note that as a non-commerial OpenSource project we are not able to pay bounties at the moment.
+Please note that as a non-commercial OpenSource project we are not able to pay bounties at the moment.