common: Update language chooser dialog title and buttons to match design

Update to use "Select Language" and "Select" as per:
https://wiki.gnome.org/Design/SystemSettings/RegionAndLanguage
11 jobs for <span class="ref-name">common-language-chooser-title</span> in 4 minutes and 42 seconds (queued for 47 seconds)
Status Job ID Name Coverage
  Build
passed #104157
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  Test
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passed #104158
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manual #104164
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armv8
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flatpak
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msan
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ppc64le
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tsan
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ubsan
 
  Review
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review
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