Re-enable previously disabled test for DevTools roll

Disabling CL: https://chromium-review.googlesource.com/c/chromium/src/+/2235718
DevTools CL: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2236400

Bug: 946975
Change-Id: Ib0b84bda186ed009b36f587ecfd540f2310e61bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236138
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776526}

third_party/blink/web_tests/TestExpectations

@@ -1889,7 +1889,6 @@ crbug.com/1075869 http/tests/devtools/elements/styles-1/color-swatch.js [ Pass F
 crbug.com/1075869 http/tests/devtools/elements/styles-3/spectrum.js [ Pass Failure ]
 crbug.com/1075869 http/tests/devtools/elements/styles-4/styles-invalid-color-values.js [ Pass Failure ]
 crbug.com/1075869 http/tests/devtools/extensions/extensions-timeline-api.js [ Pass Failure Timeout ]
-crbug.com/946975 http/tests/devtools/sources/autocomplete-css.js [ Pass Failure ]
 
 # On these platforms (all but Android) media tests don't currently use gpu-accelerated (proprietary) codecs, so no
 # benefit to running them again with gpu acceleration enabled.