update region list

Author: cachai2

articles/azure-functions/functions-premium-plan.md

@@ -197,10 +197,6 @@ See the complete regional availability of Functions on the [Azure web site](http
 |USGov Arizona| 100 | 20 |
 |USGov Texas| 100 | Not Available |
 |USGov Virginia| 100 | 20 |
-|USNat East| 100 | Not Available |
-|USNat West| 100 | Not Available |
-|USSec East| 100 | 20 |
-|USSec West| 100 | 20 |
 |West Central US| 100 | 20 |
 |West Europe| 100 | 20 |
 |West India| 100 | 20 |