update v71.go to resolve #5595

[nephatrine]

I opened issue #5595 after experiencing a hang while updating to a new gitea version during db migration protecting the scratch tokens. On the advice of user @typeless this incredibly simple change resolved the issue. I did not find any unwanted side effects from this and everything including 2-factor seems to be working on my test gitea instance post-update.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@64995ba). Click here to learn what that means.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #5613   +/-   ##
=========================================
  Coverage          ?   37.53%           
=========================================
  Files             ?      322           
  Lines             ?    47458           
  Branches          ?        0           
=========================================
  Hits              ?    17811           
  Misses            ?    27094           
  Partials          ?     2553

Impacted Files	Coverage Δ
models/migrations/v71.go	0% <0%> (ø)

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