Reduce directories excerpter tool gets fragments from (#10260)

This fixes some issues with unrelated files having unexpected formats
when running locally, and results in slightly faster refresh excerpt
times.

Author: parlough

build.excerpt.yaml

@@ -3,10 +3,6 @@ targets:
     sources:
       include:
         - examples/**
-        # Some default includes that aren't really used here but will prevent
-        # false-negative warnings:
-        - $package$
-        - lib/$lib$
       exclude:
         - '**/.*/**'
         - '**/android/**'