Update message description so no it no longer uses problematic language

As part of the work replacing offensive language usage, we need to update the following help message that is output by the Elytron Tool since it describes the -v argument with the following text:

-v,--alias <arg>                               Vault master key alias within key store (defaults to "vault")

 
The source for the message can be found here:

https://github.com/wildfly-security/wildfly-elytron/blob/1.x/tool/src/main/java/org/wildfly/security/tool/ElytronToolMessages.java#L257

We need to update this message so that it no longer mentions "master". The message should simply be: 

Vault key alias within key store (defaults to "vault")