[ci] Pin master for LUCI tests (#4681)

Update LUCI to match recent Cirrus change, using a pinned version of
master instead of latest master.

Part of flutter/flutter#93811

.ci.yaml

@@ -41,6 +41,8 @@ targets:
     properties:
       add_recipes_cq: "true"
       target_file: windows_build_and_platform_tests.yaml
+      channel: master
+      version_file: flutter_master.version
       dependencies: >
         [
           {"dependency": "vs_build"}
@@ -66,6 +68,8 @@ targets:
     properties:
       add_recipes_cq: "true"
       target_file: build_all_plugins.yaml
+      channel: master
+      version_file: flutter_master.version
       dependencies: >
         [
           {"dependency": "vs_build"}
@@ -91,6 +95,8 @@ targets:
     properties:
       add_recipes_cq: "true"
       target_file: uwp_build_and_platform_tests.yaml
+      channel: master
+      version_file: flutter_master.version
       dependencies: >
         [
           {"dependency": "vs_build"}
@@ -103,6 +109,8 @@ targets:
     properties:
       add_recipes_cq: "true"
       target_file: plugin_tools_tests.yaml
+      channel: master
+      version_file: flutter_master.version
     scheduler: luci
 
   - name: Linux ci_yaml plugins roller