Unskip fast/css/font-family-case-insensitive.html

The flaky lower-case font matching ("ahem") has been fixed in
https://crrev.com/c/1249385 , so we can unskip this test now.

Bug: 724392
Change-Id: I2a005fe055684aa9e8662a0324a6f7ad84935a1a
Reviewed-on: https://chromium-review.googlesource.com/1249276Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594886}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4155,7 +4155,6 @@ crbug.com/718155 payments/payment-request-in-iframe.html [ Failure ]
 crbug.com/718155 payments/payment-request-in-iframe-nested-not-allowed.html [ Failure ]
 
 # Layout Tests on Swarming (Windows) - https://crbug.com/717347
-crbug.com/724392 [ Win ] fast/css/font-family-case-insensitive.html [ Failure Pass Timeout ]
 crbug.com/713094 [ Win ] fast/css/fontfaceset-check-platform-fonts.html [ Failure Pass ]
 
 # Image decode failures due to document destruction.