cask/installer: fix reference to opt_linked/optlinked

[SeekingMeaning]

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---

opt_linked? does not exist and should instead be optlinked?

grep output for references to opt_linked:

$ grep -r 'opt_linked' .                 
./Library/Homebrew/cask/installer.rb:        installed && (cask_or_formula.respond_to?(:opt_linked?) ? cask_or_formula.opt_linked? : true)

Possible alternative:

• Change this:

installed = if cask_or_formula.respond_to?(:any_version_installed?)
  cask_or_formula.any_version_installed?
else
  cask_or_formula.try(:installed?)
end
installed && (cask_or_formula.respond_to?(:opt_linked?) ? cask_or_formula.opt_linked? : true)

• to this:

if cask_or_formula.is_a?(Formula)
  cask_or_formula.any_version_installed? && cask_or_formula.optlinked?
else
  cask_or_formula.installed?
end

[MikeMcQuaid]

Good catch, thanks @SeekingMeaning!