Bump dugite to 1.104.0

[alexrudd2]

The included version of dugite pulls in an old version of git itself, which causes plenty of problems on new installs.

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Description of the Change

The included version of dugite pulls in an old version of git itself, which causes plenty of problems on new installs.

Screenshot or Gif

N/A

Applicable Issues

(probably) closes https://github.com/atom/github/issues/2720