infra: Move RBE FYI CrOS builder to "prod" category in Milo

This is to be built on the Goma RBE Prod backend:
https://chromium-review.googlesource.com/c/chromium/tools/build/+/1886131

Bug: 947436
Change-Id: I5a40c2b2113bf17e8d01b56e33e62dbfbbacdf0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1886074
Auto-Submit: Simon Que <sque@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710222}

infra/config/consoles/chromium.goma.fyi.star

@@ -74,7 +74,7 @@ luci.console_view(
         ),
         luci.console_view_entry(
             builder = 'ci/chromeos-amd64-generic-rel (Goma RBE FYI)',
-            category = 'tot|chromium.chromiumos|simple|release|x64',
+            category = 'prod|chromium.chromiumos|simple|release|x64',
             short_name = 'rel',
         ),
     ],

infra/config/generated/luci-milo.cfg

@@ -4139,7 +4139,7 @@ consoles: <
   >
   builders: <
     name: "buildbucket/luci.chromium.ci/chromeos-amd64-generic-rel (Goma RBE FYI)"
-    category: "tot|chromium.chromiumos|simple|release|x64"
+    category: "prod|chromium.chromiumos|simple|release|x64"
     short_name: "rel"
   >
   header: <