commands: remove diy, add lc alias for livecheck

[nandahkrishna]

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This PR makes two minor changes:

• It removes the default alias for brew diy (configure) which no longer exists.
• It adds lc as a default alias for livecheck, similar to tc for typecheck. The reason I'm proposing this (rather than using brew alias just for myself) is because there are 7 l* commands and 4 li* commands, so at least 4 characters (i.e. liv<TAB>) are required to autocomplete to livecheck. I think users of livecheck would like having a short alias like lc, which is convenient and unambiguous (to my knowledge).

[BrewTestBot]

Review period will end on 2021-07-15 at 16:38:44 UTC.

[BrewTestBot]

Review period ended.