change(core): Updated at core version to 7b6d97b5

- fix(blufi): Fixed a blufi memory leak issue
- fix(ble): Fixed AT+BLECONN query returns ERROR when ble is not initialized on bluedriod
- fix(ble): Fixed missing ble scan result issue when AT works as ble dual role on bluedriod
- Closes ESPAT-2584, ESPAT-2585, ESPAT-2592

Author: ustccw

components/at/lib/VERSION

@@ -1,7 +1,7 @@
-ESP32:   48d94ba
-ESP32C3: 48d94ba
-ESP32C2: 48d94ba
-ESP32C5: 48d94ba
-ESP32C6: 48d94ba
-ESP32C61:48d94ba
-ESP32S2: 48d94ba
+ESP32:   7b6d97b
+ESP32C3: 7b6d97b
+ESP32C2: 7b6d97b
+ESP32C5: 7b6d97b
+ESP32C6: 7b6d97b
+ESP32C61:7b6d97b
+ESP32S2: 7b6d97b