Fixed example for Table.upsert()

[ghost]

Fixes #<issue_number_goes_here> (it's a good idea to open an issue first for discussion)

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@30db9ae). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #533   +/-   ##
=========================================
  Coverage          ?   89.76%           
=========================================
  Files             ?       15           
  Lines             ?     1417           
  Branches          ?       42           
=========================================
  Hits              ?     1272           
  Misses            ?      140           
  Partials          ?        5

Impacted Files	Coverage Δ
src/table.ts	100% <ø> (ø)

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[callmehiphop]

Thanks for the fix @sulaysumaria!