[pm/incremental] remove LauncherActivityInfo.isStartable()

This API is not needed because any installed app is startable. See
go/incremental-when-to-freeze for detailed discussion.

BUG: 171299283
BUG: 171920377
Test: atest LauncherAppsSingleUserTest
Change-Id: I665b1005780babd02677a0f4ad8284ac81a5502e

api/current.txt

@@ -11735,7 +11735,6 @@ package android.content.pm {
     method public float getLoadingProgress();
     method public String getName();
     method public android.os.UserHandle getUser();
-    method public boolean isStartable();
   }
 
   public class LauncherApps {

core/api/current.txt

@@ -11735,7 +11735,6 @@ package android.content.pm {
     method public float getLoadingProgress();
     method public String getName();
     method public android.os.UserHandle getUser();
-    method public boolean isStartable();
   }
 
   public class LauncherApps {

core/java/android/content/pm/LauncherActivityInfo.java

@@ -83,13 +83,6 @@ public class LauncherActivityInfo {
         return mInternal.getActivityInfo().loadLabel(mPm);
     }
 
-    /**
-     * @return whether the package is startable.
-     */
-    public boolean isStartable() {
-        return mInternal.getIncrementalStatesInfo().isStartable();
-    }
-
     /**
      * @return Package loading progress, range between [0, 1].
      */