Lock GPU Windows NVIDIA to 1909

Locks the GPU Windows 10 NVIDIA machines to Windows 10 1909 and the
newer driver version since the upgrade is complete.

TBR=ynovikov@chromium.org

Bug: 1085489
Change-Id: I22a9c06309ab33585de71c5d700f10d588957169
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2385983Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803227}

testing/buildbot/mixins.pyl

@@ -849,8 +849,8 @@
   'win10_nvidia_quadro_p400_stable': {
     'swarming': {
       'dimensions': {
-        'gpu': '10de:1cb3-26.21.14.3102|10de:1cb3-27.21.14.5148',
-        'os': 'Windows-10|Windows-10-18363',
+        'gpu': '10de:1cb3-27.21.14.5148',
+        'os': 'Windows-10-18363',
         'pool': 'chromium.tests.gpu',
       },
     },
@@ -862,8 +862,8 @@
     'swarming': {
       'dimension_sets': [
         {
-          'gpu': '10de:1cb3-26.21.14.3102|10de:1cb3-27.21.14.5148',
-          'os': 'Windows-10|Windows-10-18363',
+          'gpu': '10de:1cb3-27.21.14.5148',
+          'os': 'Windows-10-18363',
           'pool': 'chromium.tests.gpu',
         },
       ],