enable test for react tsx sourcemaps

[cspotcode]

I kept seeing this test disables, so I enabled it. I don't know if it was meant to test something else.

[codecov]

Codecov Report

Merging #1088 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1088   +/-   ##
=======================================
  Coverage   75.08%   75.08%           
=======================================
  Files           6        6           
  Lines         606      606           
  Branches      141      141           
=======================================
  Hits          455      455           
  Misses        100      100           
  Partials       51       51           

Flag	Coverage Δ
#node_10	72.15% <ø> (-0.20%)	⬇️
#node_12_15	72.74% <ø> (ø)
#node_12_16	72.74% <ø> (ø)
#node_13	74.58% <ø> (-0.17%)	⬇️
#node_14	74.75% <ø> (-0.17%)	⬇️
#typescript_2_7	74.58% <ø> (ø)
#typescript_latest	73.76% <ø> (ø)
#typescript_next	73.59% <ø> (ø)
#ubuntu	74.58% <ø> (-0.17%)	⬇️
#windows	74.91% <ø> (ø)

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[coveralls]

Coverage increased (+1.03%) to 82.99% when pulling 1cae13a on ab/enable-react-tsx-sourcemap-test into b3f84bc on master.