[committed] Add check_vect in a testcase

Also reformat a comment that had too long lines.
Commit c5bd0e58 introduced both these problems to fix.

Committed as obvious after ensuring that when running the testcase on
AArch64 it still fails before the original c5bd0e58 commit and passes
after it.

gcc/ChangeLog:

	* tree-vect-stmts.cc (get_group_load_store_type): Reformat
	comment.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/vect-multi-peel-gaps.c: Add `check_vect` call into
	`main` of this testcase.