Tag Alias: happy_valentine -> valentine

Aliasing happy_valentine -> valentine.

Reason: Same concept.

I think a difference could be drawn between the two, like the difference between happy_birthday and birthday. Where happy birthday is used for where the greeting "Happy Birthday" is used in the image and birthday is used for any image related to celebrating a birthday.

If we can find more than a few that say "happy valentine" then maybe we can separate, otherwise I'd prefer to alias.

I've populated the happy_valentine tag with images that had "Happy Valentine" (written in so far 3 different languages), "Happy Valentine's Day", and derivatives ("Happy Sweet Valentine," "Happy St. Valentine's Day," "Happy Van Allen Radiation Belt" (Vu~an Aren-tai), etc). The tag is now up to 565 posts (18.8% of the Valentine images).