SB2209 RP2204 gpio21 and gpio22 always triggered

I am trying to connect filament sensors to GPIO21 and GPIO22, but the sensor signal does not change when they are triggered.

```
`[filament_switch_sensor Aft_Extruder]
pause_on_runout: false
# When set to True, a PAUSE will execute immediately after a runout
# is detected. Note that if pause_on_runout is False and the
# runout_gcode is omitted then runout detection is disabled. Default
# is True.
runout_gcode:
PAUSE
RESPOND TYPE=error MSG="Обнаружено отсутствие прутка после экструдера"
# A list of G-Code commands to execute after a filament runout is
# detected. See docs/Command_Templates.md for G-Code format. If
# pause_on_runout is set to True this G-Code will run after the
# PAUSE is complete. The default is not to run any G-Code commands.
insert_gcode:
RESPOND TYPE=error MSG="Обнаружена подача прутка"
# A list of G-Code commands to execute after a filament insert is
# detected. See docs/Command_Templates.md for G-Code format. The
# default is not to run any G-Code commands, which disables insert
# detection.
event_delay: 3
# The minimum amount of time in seconds to delay between events.
# Events triggered during this time period will be silently
# ignored. The default is 3 seconds.
#pause_delay: 0.5
# The amount of time to delay, in seconds, between the pause command
# dispatch and execution of the runout_gcode. It may be useful to
# increase this delay if OctoPrint exhibits strange pause behavior.
# Default is 0.5 seconds.
switch_pin: EBBCan:gpio21
# The pin on which the switch is connected. This parameter must be
# provided.`
```
I can't use GPIO6 or the Xlimin pin as a workaround because they are already in use.

I have several SB2209 RP2204 boards, and I am experiencing the same issue with all of them.

Start by reproducing the reported behavior with the supplied filament_switch_sensor configuration on GPIO21 and GPIO22 across the SB2209 RP2204 boards. Compare those pins with the GPIO6 and Xlimin workaround mentioned in the report; the issue is done when the sensor signal changes reliably on GPIO21 and GPIO22 or the pin limitation is documented.

Written by the indexing model from the issue text.