Roll buildroot to pick change to cppwinrt invocation (flutter/engine#25993)

* Roll buildroot to pick change to cppwinrt invocation

* disable uwp builders

DEPS

@@ -96,7 +96,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + '45ce223bc8d8ca88e2eb2f38eb0cf799e39edd06',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + '7137efc8964bd91fa13e69af2cd3d1e13007d065',
 
    # Fuchsia compatibility
    #
@@ -662,7 +662,7 @@ hooks = [
     'pattern': '.',
     'condition': 'download_windows_deps',
     'action': [
-      'python',
+      'python3',
       'src/build/win/generate_winrt_headers.py',
     ]
   }

engine/src/flutter/ci/dev/prod_builders.json

@@ -68,10 +68,6 @@
          "name":"Windows Host Engine",
          "repo":"engine"
       },
-      {
-         "name":"Windows UWP Engine",
-         "repo":"engine"
-      },
       {
          "name":"Windows Web Engine",
          "repo":"engine"

engine/src/flutter/ci/dev/try_builders.json

@@ -110,7 +110,7 @@
       {
          "name":"Windows UWP Engine",
          "repo":"engine",
-         "enabled": true
+         "enabled": false
       },
       {
          "name":"Windows Web Engine",