Clear apex.go entries for bluetooth libs

The module availability to Bluetooth is currently hard-coded in apex.go.
We are in the process of cleaning the apex.go by adding the availability
in each required module

Test: Build + TH + boot phone & use bluetooth
Bug: 216433795
Change-Id: I5cef83d960ae56104a41356c00867cebd54f0c5d
diff --git a/librilutils/Android.bp b/librilutils/Android.bp
index 1d39eaf..00df7ce 100644
--- a/librilutils/Android.bp
+++ b/librilutils/Android.bp
@@ -45,4 +45,8 @@
     },
     min_sdk_version: "30",
     sdk_version: "current",
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.bluetooth",
+    ],
 }