Do not try and enhance MySQL Prompt in Linux

[nickvanw]

We're not confident that we can do this the way that we want, so we'll leave it as the default for now. Same as Windows.

[nickvanw]

~> go test ./...
?   	github.com/planetscale/cli/cmd/pscale	[no test files]
ok  	github.com/planetscale/cli/internal/auth	(cached)
?   	github.com/planetscale/cli/internal/cmd	[no test files]
?   	github.com/planetscale/cli/internal/cmd/auth	[no test files]
ok  	github.com/planetscale/cli/internal/cmd/backup	(cached)
ok  	github.com/planetscale/cli/internal/cmd/branch	(cached)
?   	github.com/planetscale/cli/internal/cmd/connect	[no test files]
ok  	github.com/planetscale/cli/internal/cmd/database	(cached)
ok  	github.com/planetscale/cli/internal/cmd/deployrequest	(cached)
ok  	github.com/planetscale/cli/internal/cmd/org	(cached)
ok  	github.com/planetscale/cli/internal/cmd/shell	(cached)
?   	github.com/planetscale/cli/internal/cmd/signup	[no test files]
ok  	github.com/planetscale/cli/internal/cmd/token	(cached)
?   	github.com/planetscale/cli/internal/cmd/version	[no test files]
?   	github.com/planetscale/cli/internal/cmdutil	[no test files]
?   	github.com/planetscale/cli/internal/config	[no test files]
ok  	github.com/planetscale/cli/internal/dumper	(cached)
?   	github.com/planetscale/cli/internal/mock	[no test files]
?   	github.com/planetscale/cli/internal/printer	[no test files]
?   	github.com/planetscale/cli/internal/promptutil	[no test files]
?   	github.com/planetscale/cli/internal/proxyutil	[no test files]
?   	github.com/planetscale/cli/internal/testutil	[no test files]
ok  	github.com/planetscale/cli/internal/update	(cached)