Build API stub with less number of source files

The metalava fix 09094fc5e566a380b7aa1a4c3948ac66cebc0aba allows us to
not include source files having class definitions that are referenced by
private constructors of the API classes.

Removing the now uncessary source files from the input list so that
metalava can run faster.

Bug: 141149570
Test: m
Change-Id: Ib203221600baa0e57393b0d448125676d01bcb8e