Remove experimental immersive mode support. DO NOT MERGE

Bug: 2949215

Change-Id: I7d998ef571ef7e149bb96261430e92150b80b77d

api/current.xml

@@ -26633,17 +26633,6 @@
  visibility="public"
 >
 </field>
-<field name="FLAG_HIGH_PRIORITY"
- type="int"
- transient="false"
- volatile="false"
- value="128"
- static="true"
- final="true"
- deprecated="not deprecated"
- visibility="public"
->
-</field>
 <field name="FLAG_INSISTENT"
  type="int"
  transient="false"
@@ -46071,17 +46060,6 @@
  visibility="public"
 >
 </field>
-<field name="FLAG_IMMERSIVE"
- type="int"
- transient="false"
- volatile="false"
- value="512"
- static="true"
- final="true"
- deprecated="not deprecated"
- visibility="public"
->
-</field>
 <field name="FLAG_MULTIPROCESS"
  type="int"
  transient="false"