Fix wrong reference to --autofill instead of --fill in docs

[profclems]

Closes #651

[codecov]

Codecov Report

Merging #653 (fa35e2a) into trunk (4baffeb) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##            trunk     #653   +/-   ##
=======================================
  Coverage   60.05%   60.05%           
=======================================
  Files          90       90           
  Lines        6431     6431           
=======================================
  Hits         3862     3862           
  Misses       2206     2206           
  Partials      363      363           

Impacted Files	Coverage Δ
commands/mr/create/mr_create.go	28.76% <100.00%> (ø)

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