Add comment to series files indicating that the following bug fix

Add comment to series files indicating that the following bug fix
patches have been posted to Linus, and thus should not be modified ---
since after -rc5 has been released, they will be deleted as part of
the rebase to -rc5:

ext4_unwritten_extent_delalloc_fix.patch
ext4-fix-no-extent-truncate-i_prealloc-bug
fix-delalloc-release-block-reservation-for-truncate
dx_readdir_hash_collision_fix.patch
ext4-use-generic-discard-reservations-call
dont-try-to-resize-if-there-are-no-reserved-gdt-blocks-left.patch
fix-flex_bg-ialloc
JC1-journal_credit_fix_for_nonextent.patch
JC2-journal_credit_for_extents_fix.patch
JC3-journal_credit_fix_for_dio_fallocate.patch
JC4-da_writepages_rework.patch
JC5-da_writepages_credit_fix.patch
ext4_has_free_blocks_fix.patch
ext4_alloc_inode_initialize_writeback_index.patch
fix-small-file-fragmentation
ext4__update_documentation_to_remind_users_to_update_mke2fs.conf