Bump version to 2.1.0-alpha #2

Job	Run time
Flatpak	2h 23m 49s
Build All (macos-12, x86_64) / Check Cache	18s
Build All (windows-latest) / Check Cache	23s
Build All (ubuntu-20.04) / Check Cache	12s
Build All (macos-12, arm64) / Check Cache	16s
Build All (ubuntu-20.04) / Build Deps / Build Deps	36m 23s
Build All (macos-12, arm64) / Build Deps / Build Deps	50m 52s
Build All (macos-12, x86_64) / Build Deps / Build Deps	41m 51s
Build All (windows-latest) / Build Deps / Build Deps	43m 53s
Build All (ubuntu-20.04) / Build Deps / Build OrcaSlicer / Build OrcaSlicer	44m 16s
Build All (macos-12, x86_64) / Build Deps / Build OrcaSlicer / Build OrcaSlicer	29m 20s
Build All (windows-latest) / Build Deps / Build OrcaSlicer / Build OrcaSlicer	49m 20s
Build All (macos-12, arm64) / Build Deps / Build OrcaSlicer / Build OrcaSlicer	25m 31s
	7h 46m 24s

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