chore(base): Rename from_sync_v3 to …_v2.

The version of something is 3 but the sync version is 2. Confusing.

crates/matrix-sdk-base/src/client.rs

@@ -858,7 +858,7 @@ impl BaseClient {
             let processors::e2ee::to_device::Output {
                 decrypted_to_device_events: to_device,
                 room_key_updates,
-            } = processors::e2ee::to_device::from_sync_v3(
+            } = processors::e2ee::to_device::from_sync_v2(
                 &mut context,
                 &response,
                 olm_machine.as_ref(),

crates/matrix-sdk-base/src/response_processors/e2ee/to_device.rs

@@ -53,7 +53,7 @@ pub async fn from_msc4186(
 ///
 /// This returns a list of all the to-device events that were passed in but
 /// encrypted ones were replaced with their decrypted version.
-pub async fn from_sync_v3(
+pub async fn from_sync_v2(
     context: &mut Context,
     response: &v3::Response,
     olm_machine: Option<&OlmMachine>,