doc: Raspberry Pi Pico board page document fix for pwm

There was problem a format mistake on Supported Features table last
element pwm. Fixed by removing spaces and adding option

Signed-off-by: Mr. Green's Workshop <[email protected]>
Co-authored-by: Carles Cufí <[email protected]>

Author: MrGreensWorkshop

boards/arm/rpi_pico/doc/index.rst

@@ -71,8 +71,8 @@ hardware features:
      - :kconfig:option:`CONFIG_WATCHDOG`
      - :dtcompatible:`raspberrypi,pico-watchdog`
    * - PWM
-     - :kconfig: `CONFIG_PWM`
-     - :dtcompatible: `raspberrypi,pico-pwm`
+     - :kconfig:option:`CONFIG_PWM`
+     - :dtcompatible:`raspberrypi,pico-pwm`
 
 Programming and Debugging
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