upgrade to latest dependencies

bumping knative.dev/serving 1fd509b...6d9d1b6:
  > 6d9d1b6 Make autoscaler instrument async so we can remove metric attributes when revisions go away (# 16300)

Signed-off-by: Knative Automation <automation@knative.team>

Author: knative-automation

go.mod

@@ -73,7 +73,7 @@ require (
 	knative.dev/eventing v0.47.1-0.20251210120316-00f881030aaf
 	knative.dev/hack v0.0.0-20251126013634-1484a9e9b641
 	knative.dev/pkg v0.0.0-20251126013532-e853b1d1d6bb
-	knative.dev/serving v0.47.1-0.20251208151315-1fd509bf8d43
+	knative.dev/serving v0.47.1-0.20251211192118-6d9d1b67c9f7
 )
 
 require (

go.sum

@@ -1903,8 +1903,8 @@ knative.dev/networking v0.0.0-20251126213812-ebe48fd53262 h1:CEFraQgj5csZPv2NgCA
 knative.dev/networking v0.0.0-20251126213812-ebe48fd53262/go.mod h1:nxN+sYiQCoT2FLgSMTShXYmYYcb7rALHSOz6l5RjCp4=
 knative.dev/pkg v0.0.0-20250716115900-19d3cc2da0b9 h1:P9GFsqTmX4WokSVVUK1IbHOnbJLi8EW1pd4PvbUEodo=
 knative.dev/pkg v0.0.0-20250716115900-19d3cc2da0b9/go.mod h1:Hq2y1gu4P/MWEk9zB8L/zrjJ19ywEnYgwXq8ZMjRl30=
-knative.dev/serving v0.47.1-0.20251208151315-1fd509bf8d43 h1:Kp9HcIIJbHqHDkMw3rbH/MXA7ZsLZz9j5jnoo5lT544=
-knative.dev/serving v0.47.1-0.20251208151315-1fd509bf8d43/go.mod h1:olKUo5+T1KOyD4t7SM6oiEgmkVQO4Gmr6YiVwj0J944=
+knative.dev/serving v0.47.1-0.20251211192118-6d9d1b67c9f7 h1:do0rmsMlrzHpy0CfnQA1ivGEPlBc20RRF5qR8pXIuFY=
+knative.dev/serving v0.47.1-0.20251211192118-6d9d1b67c9f7/go.mod h1:olKUo5+T1KOyD4t7SM6oiEgmkVQO4Gmr6YiVwj0J944=
 rsc.io/binaryregexp v0.2.0/go.mod h1:qTv7/COck+e2FymRvadv62gMdZztPaShugOCi3I+8D8=
 rsc.io/quote/v3 v3.1.0/go.mod h1:yEA65RcK8LyAZtP9Kv3t0HmxON59tX3rD+tICJqUlj0=
 rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=