Update language to comply with inclusive guidance

Update android_app_set make files to use INSTALL rather than MASTER for
android_app_sets, this better matches the wording used for apex_set.

See https://source.android.com/setup/contribute/respectful-code for
reference

Bug: 161896447
Test: m nothing
Change-Id: I7f37a72914f4b18a839942cc3db98b1c57db921e
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index e2acf96..9d9d0e0 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -21,7 +21,7 @@
 LOCAL_APIDIFF_NEWAPI:=
 LOCAL_APIDIFF_OLDAPI:=
 LOCAL_APK_LIBRARIES:=
-LOCAL_APK_SET_MASTER_FILE:=
+LOCAL_APK_SET_INSTALL_FILE:=
 LOCAL_APKCERTS_FILE:=
 LOCAL_ARM_MODE:=
 LOCAL_ASFLAGS:=