Remove a few mozconfig entries that we set already in tor-browser.git

The mozconfig we inject to the firefox container contains a few entries we don't actually need to have there because we already set them in tor-browser.git, such as

ac_add_options --with-relative-profile=[% c('var/ProjectName') %]/Data/Browser
mk_add_options MOZ_APP_DISPLAYNAME="[% c('var/Project_Name') %]"

(well, actually I don't think we set the latter, but we can start to do it, if needed)

I think we could remove them from tor-browser-build.git.

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