Docs: Clarify allowed characters in masked variables
Docs: Clarify allowed characters in masked variables

stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq