Does not contain base RTC class like code suggests

I was looking at this library after reading the PCF85063A has the same commandset with different register offset/layout (i forget) and no century flag.

https://github.com/adafruit/Adafruit_CircuitPython_PCF8563/blob/c4ca8d355b79179b44716544577925442a801bc0/adafruit_pcf8563/pcf8563.py#L11-L12

Looks like it hasn't been true since
https://github.com/adafruit/Adafruit_CircuitPython_PCF8563/commit/4162c00d47ca9ad052df9b0f9e1d673ce0f879fc#diff-71d900ee2d75386aecc1229618618b3551f75afc2c11649aa5c18d5cd923155e

Start by reading lines 11-12 of adafruit_pcf8563/pcf8563.py and compare them with the referenced commit. Clarify whether the file still claims to provide a base RTC class, then update the relevant wording or structure so it matches the current implementation; done means the code no longer makes that inaccurate suggestion.

Written by the indexing model from the issue text.