Replace use of instance variable with local

[drjayvee]

The partial boards/edit/auto_close used both @board as well as board.

[ajaychandrak2002-bit]

please check the work flow of (boards/edit/auto_close); @board

[drjayvee]

please check the work flow of (boards/edit/auto_close); https://github.com/board

I'm not sure whether this is a bot comment. I don't understand the request or suggestion.

Here's what I did for QA:

• I tried changing board to hoard and ran the test suite, which resulted in 5 errors. (The tests pass with my change applied.)
• As far as I could tell, only two templates render this partial, both of which pass the board local.
• The partial already uses (and therefore depends on) a local board. It's extremely unlikely that @board and board would ever be two different models.

[monorkin]

Good catch @drjayvee ! Thank you for the PR.