Reset default sample rate; update simpletest example

Restored the default ADC conversion rate to 10 samples per second after eliminating a racing condition caused by a fixed delay in the driver's channel setter. The setter now waits for the Cycle Ready (CR) flag. Successfully tested channel setting for all conversion rates. Note: high sample rates are inherently less accurate but may be useful for some applications.

Updated nau7802_simpletest.py to wait for the CR flag when acquiring data.

Both changes are expected to be transparent to all existing applications.

Also remove the outdated Clue Scale examples. They have been replaced by the Adafruit Clue Scale guide.

Thank you to @Swicano for discovering the initial issue in nau7802_simpletest.py that revealed the timing problem.