DoNotConvert tzdata nor tz_version

In using prebuilt_file for prebuilt_{etc,usr_share}, Bazel now sees such
targets translated and doesn't permit a target name to alias e.g. its
`src`. Thus we temporarily disable the conversion of the `tz_version` and
`tzdata` whilst their in-tree sources are updated. Their conversions
will be reenabled afterward.

Bug: 215723302
Test: bp2build.sh
Test: mixed_{libc,droid}.sh
Change-Id: Ie19813ccb0fb93c90b54bfd19c909ed15b826385