Do not write avb_*_key_path of android_filesystem to misc_info.txt

This matches the make packaging system implementaton.

avb_*_key_path of bootimg, vbmeta and system_other will continue to be
written to Soong built misc_info.txt

Bug: 398036609
Test: Built and diff'd locally
Change-Id: Ie2d4ad8362ce7f44d473ef185562c60718e173b3