Increase GF dynamic partition size to 8G

Bug: 235574341
Bug: 258783815
Test: $ lunch sdk_phone64_x86_64-userdebug; m
      $ ls -l $OUT/super.img - check 8G
      $ grep -i dynamic_partitions_group_size $OUT/misc_info.txt

(cherry picked from commit bb8e6f5b)
Merged-In: Ib08ee42e76a91b1c61c1b870f890dba66ed61209
Change-Id: I6c3ef94f9f08f42bd1edd01ff740d00c8d870e33