Change GPU driver bug list tag from windows to win

Some recent additions to gpu_driver_bug_list.json tagged the workarounds
with os type "windows" when "win" is the correct tag. This fixes that.

I'll investigate adding checks to the script to reject unknown OS types.

Bug: 775898,785648
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I4f9cfb86487385c45fe6a2a8f67c93f711c0f315
Reviewed-on: https://chromium-review.googlesource.com/791850Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519916}

gpu/config/gpu_driver_bug_list.json

@@ -2706,7 +2706,7 @@
       "description": "Direct composition causes slow presents on Intel Sandybridge",
       "cr_bugs": [775898, 785648],
       "os": {
-        "type": "windows"
+        "type": "win"
       },
       "vendor_id": "0x8086",
       "device_id": ["0x0116"],
@@ -2719,7 +2719,7 @@
       "description": "Direct composition causes slow presents on old Nvidia GPUs",
       "cr_bugs": [775898],
       "os": {
-        "type": "windows"
+        "type": "win"
       },
       "vendor_id": "0x10de",
       "device_id": ["0x10d8"],