ci/install-depends: attempt to fix "brew cask" stuff

We run "git pull" against "$cask_repo"; clarify that we are
expecting not to have any of our own modifications and running "git
pull" to merely update, by passing "--ff-only" on the command line.

Also, the "brew cask install" command line triggers an error message
that says:

    Error: Calling brew cask install is disabled! Use brew install
    [--cask] instead.

In addition, "brew install caskroom/cask/perforce" step triggers an
error that says:

    Error: caskroom/cask was moved. Tap homebrew/cask instead.

Attempt to see if blindly following the suggestion in these error
messages gets us into a better shape.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/install-dependencies.sh

@@ -44,13 +44,13 @@ osx-clang|osx-gcc)
 	test -z "$BREW_INSTALL_PACKAGES" ||
 	brew install $BREW_INSTALL_PACKAGES
 	brew link --force gettext
-	brew cask install --no-quarantine perforce || {
+	brew install --cask --no-quarantine perforce || {
 		# Update the definitions and try again
 		cask_repo="$(brew --repository)"/Library/Taps/homebrew/homebrew-cask &&
-		git -C "$cask_repo" pull --no-stat &&
-		brew cask install --no-quarantine perforce
+		git -C "$cask_repo" pull --no-stat --ff-only &&
+		brew install --cask --no-quarantine perforce
 	} ||
-	brew install caskroom/cask/perforce
+	brew install homebrew/cask/perforce
 	case "$jobname" in
 	osx-gcc)
 		brew install gcc@9