fix scanvi predict typo

[galenxing]

fixes #1092

[codecov]

Codecov Report

Merging #1100 (1d67591) into master (ba22825) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1100   +/-   ##
=======================================
  Coverage   90.66%   90.66%           
=======================================
  Files          91       91           
  Lines        6908     6908           
=======================================
  Hits         6263     6263           
  Misses        645      645           

Impacted Files	Coverage Δ
scvi/model/_scanvi.py	93.80% <100.00%> (ø)

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[adamgayoso]

Also we should add a test...