Revert "[HOTFIX] Disable dead bots"

This reverts commit 4654f2b60f7a3fdb1a84d39d6504ba57be77f863.

Reason for revert: Bots are alive again.

Original change's description:
> [HOTFIX] Disable dead bots
>
> All of the luci.flex.try arm64 bots and all of the luci.flex.ci 18.04
> arm64 bots have all died without warning.
>
> This patch disables the corresponding builders until the P0 bug
> referenced is resolved.
>
> TBR=mfoltz@chromium.org
>
> Bug: 1154014
> Change-Id: If544b8673ae7993374d67405f2c918315bd4bf57
> Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/2566740
> Reviewed-by: Jordan Bayles <jophba@chromium.org>

TBR=mfoltz@chromium.org,jophba@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1154014
Change-Id: If4cfd6042d2b8a79daefea2ce9f9668fd4ef853c
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/2569621
Reviewed-by: Jordan Bayles <jophba@chromium.org>
diff --git a/infra/config/global/cr-buildbucket.cfg b/infra/config/global/cr-buildbucket.cfg
index 0596923..7a60c48 100644
--- a/infra/config/global/cr-buildbucket.cfg
+++ b/infra/config/global/cr-buildbucket.cfg
@@ -235,17 +235,15 @@
       mixins: "goma_rbe_ats"
     }
 
-    # HOTFIX for missing ARM64 bots.
-    # TODO(crbug.com/1154014): ARM64 bots have all been deleted.
-    # builders {
-    #   name: "linux_arm64_debug"
-    #   mixins: "linux"
-    #   mixins: "arm64"
-    #   mixins: "debug"
-    #   mixins: "sysroot_platform_stretch"
-    #   mixins: "ci"
-    #   mixins: "goma_rbe_ats"
-    # }
+    builders {
+      name: "linux_arm64_debug"
+      mixins: "linux"
+      mixins: "arm64"
+      mixins: "debug"
+      mixins: "sysroot_platform_stretch"
+      mixins: "ci"
+      mixins: "goma_rbe_ats"
+    }
 
     builders {
       name: "mac_debug"
@@ -347,16 +345,14 @@
       mixins: "goma_rbe_ats"
     }
 
-    # HOTFIX for missing ARM64 bots.
-    # TODO(crbug.com/1154014): ARM64 bots have all been deleted.
-    # builders {
-    #   name: "linux_arm64_debug"
-    #   mixins: "linux"
-    #   mixins: "arm64"
-    #   mixins: "debug"
-    #   mixins: "sysroot_platform_stretch"
-    #   mixins: "goma_rbe_ats"
-    # }
+    builders {
+      name: "linux_arm64_debug"
+      mixins: "linux"
+      mixins: "arm64"
+      mixins: "debug"
+      mixins: "sysroot_platform_stretch"
+      mixins: "goma_rbe_ats"
+    }
 
     builders {
       name: "mac_debug"