Clearer text about double tapping reset only working for boot after already having QMK running in board (#23042)

Co-authored-by: Drashna Jaelre <drashna@live.com>

docs/flashing.md

@@ -464,4 +464,4 @@ CLI Flashing sequence:
 3. Flash via QMK CLI eg. `qmk flash --keyboard handwired/onekey/rpi_pico --keymap default`
 4. Wait for the keyboard to become available
 
-<sup>1</sup>: This works only if QMK was compiled with `RP2040_BOOTLOADER_DOUBLE_TAP_RESET` defined.
+<sup>1</sup>: This works only if the controller has been flashed with QMK Firmware with `RP2040_BOOTLOADER_DOUBLE_TAP_RESET` defined.