fix two pico_audio links

Author: tannewt

README.md

@@ -11,8 +11,8 @@ Library|Description
 [hardware_rosc](src/rp2_common/hardware_rosc)| API for the ring oscillator
 [lwip](src/rp2_common/lwip)| [LWIP Lightweight IP Library](https://savannah.nongnu.org/projects/lwip/) packed as an INTERFACE library for use with the Pico SDK
 [pico_audio](src/common/pico_audio)|Audio output support; this is highly functional, but the API is subject to change 
-   [pico_audio_i2s](src/rp2_common/pico_audio_spdif)|Audio output via I2S on 3 GPIOs using PIO. Arbitrary frequency
-   [pico_audio_pwm](src/rp2_common/pico_audio_spdif)|Audio output via (PIO) PWM. Currently a bit limited in frequency support (it was developed on FPGA to do 22050Hz at 48Mhz system clock). It does however support error diffusion dithering and noise shaping with 16x oversampling to give surprsingly good audio quality. This code will be split to provide both a fixed frequencie(s) version and a slightly slower but rather better arbitrary frequency version supporting ever higher carrier frequencies 
+   [pico_audio_i2s](src/rp2_common/pico_audio_i2s)|Audio output via I2S on 3 GPIOs using PIO. Arbitrary frequency
+   [pico_audio_pwm](src/rp2_common/pico_audio_pwm)|Audio output via (PIO) PWM. Currently a bit limited in frequency support (it was developed on FPGA to do 22050Hz at 48Mhz system clock). It does however support error diffusion dithering and noise shaping with 16x oversampling to give surprsingly good audio quality. This code will be split to provide both a fixed frequencie(s) version and a slightly slower but rather better arbitrary frequency version supporting ever higher carrier frequencies 
    [pico_audio_spdif](src/rp2_common/pico_audio_spdif)|Audio output in S/PDIF on a GPIO using PIO. Supports up to 192khz stereo. Consumed OK in test, haven't tried it with real hardware
 [pico_sd_card](src/rp2_common/pico_sd_card)|1 and 4 bit SDIO support using PIO. This is functional (currently writing is only 1 bit), but the the code is very much prototype and the API is just a placeholder - the command set needs to be separated from the SDIO and shared with SPI
 [pico_sleep](src/rp2_common/pico_sleep)|Low power related APIs, WIP because they are not sufficiently generic and also only handle core 0