fix(bash): fix duplicate diagnostics in bash pack

[lucazz]

📑 Description

While using the bash pack, I came across a this odd behavior: Bash diagnostics showing up as duplicates:

This takes place because, as referenced here and here, bash-ls has a shellcheck integration by default. So there is no need to set it up as a secondary source.

This PR removes shellcheck from the list of language servers installed by mason to be configured and used by null-ls/none-ls

[github-actions]

Review Checklist

Does this PR follow the [Contribution Guidelines](development guidelines)? Following is a partial checklist:

Proper conventional commit scoping:

• If you are adding a new plugin, the scope would be the name of the category it is being added into. ex. feat(utility): added noice.nvim plugin

• If you are modifying a pre-existing plugin or pack, the scope would be the name of the plugin folder. ex. fix(noice-nvim): fix LSP handler error

• Pull request title has the appropriate conventional commit type and scope where the scope is the name of the pre-existing directory in the project as described above

• README is properly formatted and uses fenced in links with <url> unless they are inside a [title](url)

• Proper usage of opts table rather than setting things up with the config function.

[mehalter]

LGTM