`TextFrameItem` and `TextFrameItems` types should be renamed to `TextFrame` and `TextFrames`

[smaooo]

[zlovatt]

The core classes of these objects are indeed TextFrame and TextFrames (not TextFrameItem) – however, this guide was initially created off of the "Illustrator JavaScript Scripting Reference 2017" pdf, which uses the TextFrameItem(s) naming.

I'm good to go with removing Item, but would like to open it up to any others that may want to chime in.

Keeping TextFrameItem(s):

• pro: consistency with the last Adobe-published doc
• con: name is inaccurate to internal class
• con: name is 4-5 characters longer than it needs to be (this is minor, but still)