Wrong GPIO number in hello_gpout example

[dquadros]

In the hello_gpout example, there is a mention to GPIO26 where it should GPIO25:

clock_gpio_init(26, CLOCKS_CLK_GPOUT0_CTRL_AUXSRC_VALUE_CLK_RTC, 10);

The clock_gpio_init() function accepts only GPIOs 21, 23, 24 and 25 (see https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/hardware_clocks/clocks.c)

[lurch]

ping @liamfraser