fix(deps): update dependency yargs to v12

[renovate]

This Pull Request updates dependency yargs from ^11.0.0 to ^12.0.0

Note: This PR was created on a configured schedule ("after 10pm,before 5am") and will not receive updates outside those times.

Release Notes

v12.0.0

Compare Source

Bug Fixes

• .argv and .parse() now invoke identical code path (#​1126) (f13ebf4)
• remove the trailing white spaces from the help output (#​1090) (3f0746c)
• completion: Avoid default command and recommendations during completion (#​1123) (036e7c5)

Chores

• test Node.js 6, 8 and 10 (#​1160) (84f9d2b)
• upgrade to version of yargs-parser that does not populate value for unset boolean (#​1104) (d4705f4)

Features

• add support for global middleware, useful for shared tasks like metrics (#​1119) (9d71ac7)
• allow setting scriptName $0 (#​1143) (a2f2eae)
• remove setPlaceholderKeys (#​1105) (6ee2c82)

BREAKING CHANGES

• Options absent from argv (not set via CLI argument) are now absent from the parsed result object rather than being set with undefined
• drop Node 4 from testing matrix, such that we'll gradually start drifting away from supporting Node 4.
• yargs-parser does not populate 'false' when boolean flag is not passed
• tests that assert against help output will need to be updated

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