CircuitPython_Display_Text: Update for CP7

[lesamouraipourpre]

Remove max_size usage from displayio.Group

Ref: #1603

Changes are need in the Learn Guide: https://learn.adafruit.com/circuitpython-display_text-library/overview

Page: https://learn.adafruit.com/circuitpython-display_text-library/types-of-labels
Section: Most of the page
@FoamyGuy This can have the max_size related comments removed, but the max_glyphs comments need to remain for now. There is a pending PR which will remove max_glyphs - adafruit/Adafruit_CircuitPython_Display_Text#154

[tannewt]

Thank you!

[lesamouraipourpre]

@FoamyGuy Now that max_glyphs has been removed from Display_Text Label, would you be able to rewrite the Learn Guide page below:
https://learn.adafruit.com/circuitpython-display_text-library/types-of-labels

[FoamyGuy]

Yep, thanks for the pointer. I'm in the process of making a sweep through all of the affected guides to update any references to max_glyphs, max_size, and pixel_shader in any of the code / explanations that don't get pulled from this repo. I will get this one when I am back to working on it this evenning.

[FoamyGuy]

These guide pages have been updated now.