xp.linalg.vecdot should have axis=-1 default

[oleksandr-pavlyk]

xp.linalg.vecdot is documented as alias to xp.vecdot.

However, xp.linalg.vecdot signature uses axis=None default, while xp.vecdot has axis=-1 as the default.

They should be consistent.

[kgryte]

Hmmm...this should have been fixed already: #355. The regression happened during cbbab62. I can work on a fix and backport.