Remove 'vendor_available: false'

'vendor_available: false' is used for VNDK-private libraries that
creates the vendor variants without allowing direct dependency from
the modules in vendor partition.
If the modules are not allowed to be used from any vendor modules, we
must not define this property.

Test: build
Change-Id: I0f72d2b432e2e0f6440bb186edaee96ee706f7e6
diff --git a/Android.bp b/Android.bp
index b1a9422..e8fee9a 100644
--- a/Android.bp
+++ b/Android.bp
@@ -26,7 +26,6 @@
 cc_library {
     name: "libimage_io",
     defaults: ["libimage_io-defaults"],
-    vendor_available: false,
     header_libs: ["libimage_io-headers"],
     export_include_dirs: ["includes"],
     srcs: ["src/**/*.cc"],
@@ -44,7 +43,6 @@
 cc_library_static {
     name: "libimage_io_ndk",
     defaults: ["libimage_io-defaults"],
-    vendor_available: false,
     header_libs: ["libimage_io_ndk-headers"],
     export_include_dirs: ["includes"],
     srcs: ["src/**/*.cc"],