bcachefs: Remove unneeded semicolon

./fs/bcachefs/btree_gc.c:1249:2-3: Unneeded semicolon
./fs/bcachefs/btree_gc.c:1521:2-3: Unneeded semicolon
./fs/bcachefs/btree_gc.c:1575:2-3: Unneeded semicolon
./fs/bcachefs/counters.c:46:2-3: Unneeded semicolon

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>