Clarify the help text of `--aggressive` and `--precise` of `cargo update`
Clarify the help text of `--aggressive` and `--precise` of `cargo update`

This commit makes following 2 changes:

- Replace a parameter "<name>" with "SPEC". The former is an older name
  of the latter before 0d2a2434f6f49cd671bd06e8cfc9f88bbbc67ff8.
- Document that both options make sense when used with `-p`, which
  specifies SPEC.

rust-lang/cargo,rustyhorde/cargo,nipunn1313/cargo,eminence/cargo,nipunn1313/cargo,eminence/cargo,eminence/cargo,rustyhorde/cargo,rustyhorde/cargo,rust-lang/cargo,eminence/cargo,nipunn1313/cargo,nipunn1313/cargo,rustyhorde/cargo,rust-lang/cargo,rust-lang/cargo