Log Message:
Update to 2.30.8

Changelog:
2.30.8
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* Add missing nullability annotations

* Documentation improvements

* Translation updates

2.30.7
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* Documentation fixes

2.30.6
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* Add annotations to gdk_pixbuf_save_to_buffer

* Win32 build fixes

* Translation updates

2.30.5
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* Convert documentation to markdown

* Translation updates

2.30.4
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* Make test suite robust against disabled formats

* Fix test failure when using libpng without iTXt support

* Translation updates