Rename feature gate files to use gate names

The conversion to/from snake-case was not necessary and it is
causing mental burden and extra labor in resyncing changes.

content/en/docs/reference/command-line-tools-reference/feature-gates/Accelerators.md

@@ -0,0 +1,24 @@
+---
+# Removed from Kubernetes
+title: Accelerators
+content_type: feature_gate
+
+_build:
+  list: never
+  render: false
+
+stages:
+  - stage: alpha 
+    defaultValue: false
+    fromVersion: "1.6"
+    toVersion: "1.10"
+  - stage: deprecated
+    fromVersion: "1.11"
+    toVersion: "1.11"
+
+removed: true
+---
+Provided an early form of plugin to enable Nvidia GPU support when using
+Docker Engine; no longer available. See
+[Device Plugins](/docs/concepts/extend-kubernetes/compute-storage-net/device-plugins/) for
+an alternative.

content/en/docs/reference/command-line-tools-reference/feature-gates/AppArmor.md

@@ -0,0 +1,18 @@
+---
+title: AppArmor
+content_type: feature_gate
+_build:
+  list: never
+  render: false
+
+stages:
+  - stage: beta
+    defaultValue: true
+    fromVersion: "1.4"
+    toVersion: "1.30"
+  - stage: stable
+    defaultValue: true
+    fromVersion: "1.31"
+---
+Enable use of AppArmor mandatory access control for Pods running on Linux nodes.
+See [AppArmor Tutorial](/docs/tutorials/security/apparmor/) for more details.