Update version number to 0210000000.

The Beta 2 builds (which are in dogfood an public beta) will receive modules via the Play Store with version numbers 0200000000. Hence, we must bump the version in qt-dev and hence beta 3. This is so that prebuilts in the beta 3 OTA will be higher than any Play Store pushes on beta 2. We are bumping it by 10000000 so that we have name space to do intermediate cherrypick builds if needed.

Bug: 129977903
Change-Id: I023454097f9d2948e68e91ec70dc2ed844075fde