releasetools: Make recovery patch use bsdiff exclusively

It seems like switching from minigzip to toybox gzip (bug: 288169261)
makes imgdiff fail in in this way:
* W imgdiff : imgdiff.cpp:1435 Failed to reconstruct target deflate chunk 3 []; treating as normal
* E imgdiff : imgdiff.cpp:1390 Failed to set bonus data

Test: Sign non-AB target files package
Change-Id: I29f1d8f1168347141d80860e8ed02e19b0031447