[OTA] Fix OTARequestorDriverImpl inclusion (#15981)

Former-commit-id: d5f4b0b

Author: carol-apple

config/mbed/CMakeLists.txt

@@ -456,6 +456,7 @@ endif(CONFIG_CHIP_PW_RPC)
 
 if (CONFIG_CHIP_OTA_REQUESTOR)
     target_include_directories(${APP_TARGET} PRIVATE
+        ${CHIP_ROOT}/examples/platform/mbed/ota/
         ${CHIP_ROOT}/src/app/clusters/ota-requestor
         ${CHIP_ROOT}/src/platform
         ${CHIP_ROOT}/src/platform/mbed