refactor(chat): Remove parenthesis wrapping of other files when calling `selectedCodePromptWithExtraFiles`

[ichim-david]

refactor(chat): Remove file mention duplication for default commands. Based on the comments: https://github.com/sourcegraph/cody/pull/6910#pullrequestreview-2588426217 https://github.com/sourcegraph/cody/pull/6910#issuecomment-2638393115

I'm opening this pull request in order to get rid of the extra setup parentheses between the primary mention and the other mentions. For extra context on reason see this comment https://github.com/sourcegraph/cody/pull/6910#issuecomment-2629475322

I am also removing the duplication of context mention from the default commands because these commands have been duplicated as default prompts and they do not duplicate the context mention leaving just the context mention with the file range.

Test plan

1. Run default commands such as explain code and notice the lack of context mention duplication
2. Run a prompt that uses a cody-context such as cody://current-tabs and notice that the tabs following the first tab are no longer wrapped with parenthesis