AUTOUIC: Revert "Fix generating of dependency rules for UI header files"

Revert commit e5ec0e52 (AUTOUIC: Fix generating of dependency rules
for UI header files, 2021-07-22, v3.21.1~8^2) because it caused
regressions.  For example, changing one C++ source can now cause many
others to rebuild.  Revert the change pending further investigation.

Fixes: #22531
Issue: #16776
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