Fix maximal supported MTU on Android 13 (dariuszseweryn#808)

Maximal supported MTU set to 515 since it's the maximal supported MTU since Android 13

Author: marsounjan

rxandroidble/src/main/java/com/polidea/rxandroidble2/RxBleConnection.java

@@ -56,10 +56,17 @@ public interface RxBleConnection {
     int GATT_MTU_MINIMUM = 23;
 
     /**
-     * The maximum supported value for MTU (Maximum Transfer Unit) used by a bluetooth connection on Android OS.
-     * https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/android-5.1.0_r1/stack/include/gatt_api.h#119
+     * The maximum properly supported value for MTU (Maximum Transfer Unit) used by a bluetooth connection on Android OS.
+     * <p>The theoretical maximum value for MTU Negotiation on Android OS is 517
+     * (https://cs.android.com/android/platform/superproject/+/master:packages/modules/Bluetooth/system/stack/include/gatt_api.h;l=244;drc=1918034a0730839c7a07b1260b1ab74b80d6b4e6)
+     * the real maximal supported MTU is 515 since the buffer size is capped on 512 bytes = 515 - GATT_READ_MTU_OVERHEAD
+     * (https://cs.android.com/android/platform/superproject/+/master:packages/modules/Bluetooth/system/stack/include/gatt_api.h;l=250;drc=1918034a0730839c7a07b1260b1ab74b80d6b4e6;bpv=1;bpt=1)
+     * <p>
+     * <p>NOTE: before Android 13 (API 33) the maximal properly supported MTU was 517
+     * see https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/android-5.1.0_r1/stack/include/gatt_api.h#119
      */
-    int GATT_MTU_MAXIMUM = 517;
+    int GATT_MTU_MAXIMUM = 515;
+
 
     /**
      * Description of correct values of connection priority