luacheckrc: Remove accidentally commented directive Accidentally commented in 4b258329e6e4 This directive was removed from Prosody in d59be9befad7 followed by a big sweep of the resulting warnings.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```