Remove usage of "filters" in OWNERS

The documentation states:
"WARNING: The approve plugin does not currently respect filters.
Until that is fixed, filters should only be used for the labels key (as shown in the above example)"

From now on we can only use OWNERS files per directory.

Signed-off-by: Luboslav Pivarc <[email protected]>

OWNERS

@@ -1,38 +1,9 @@
 # See the OWNERS docs at https://go.k8s.io/owners
 
-filters:
-  ".*":
-    reviewers:
-      - code-reviewers
-    approvers:
-      - approvers
-    emeritus_approvers:
-      - emeritus_approvers
-
-  "cluster-up/.*|WORKSPACE|.bazel.*|.fossa.yml|cluster-up-sha.txt":
-    reviewers:
-      - sig-buildsystem-reviewers
-    approvers:
-      - sig-buildsystem-approvers
-    labels:
-      - sig/buildsystem
-  ".*_test.go":
-    reviewers:
-      - sig-test-reviewers
-    approvers:
-       - sig-test-approvers
-    labels:
-      - sig/test
-  ".golangci.yml":
-    approvers:
-      - sig-test-approvers
-      - sig-compute-approvers
-      - sig-network-approvers
-
-  "docs/metrics.md":
-    reviewers:
-      - sig-observability-reviewers
-    approvers:
-      - sig-observability-approvers
-    labels:
-      - sig/observability
+reviewers:
+  - code-reviewers
+approvers:
+  - approvers
+emeritus_approvers:
+  - emeritus_approvers
+

cluster-up/OWNERS

@@ -0,0 +1,7 @@
+reviewers:
+  - sig-buildsystem-reviewers
+approvers:
+  - sig-buildsystem-approvers
+labels:
+  - sig/buildsystem
+

hack/OWNERS

@@ -1,17 +1,6 @@
-filters:
-
-  ".*":
-    reviewers:
-    - sig-buildsystem-reviewers
-    approvers:
-    - sig-buildsystem-approvers
-    labels:
-    - sig/buildsystem
-
-  ".*perf.*":
-    reviewers:
-      - sig-scale-reviewers
-    approvers:
-      - sig-scale-approvers
-    labels:
-      - sig/scale
+reviewers:
+- sig-buildsystem-reviewers
+approvers:
+- sig-buildsystem-approvers
+labels:
+- sig/buildsystem

staging/src/kubevirt.io/api/OWNERS

@@ -1,9 +1,4 @@
 # See the OWNERS docs at https://go.k8s.io/owners
 
-filters:
-  # examples:
-  #   pkg/api/types.go
-  #   pkg/api/*/register.go
-  "\\.go$":
-    labels:
-      - kind/api-change
+labels:
+  - kind/api-change