Copy edits: Standardize on spelling

[Julian-O]

Changed comments (only) to use American spellings of common words.

(As an Australian, it hurts me to use the American spelling, but it looks more professional to have one standard throughout, and the code itself uses American spellings, so I kept it consistent.)

Also trivial copy-edits to comments in RecycleView.

Maintainer merge checklist

• Title is descriptive/clear for inclusion in release notes.
• Applied a Component: xxx label.
• Applied the api-deprecation or api-break label.
• Applied the release-highlight label to be highlighted in release notes.
• Added to the milestone version it was merged into.
• Unittests are included in PR.
• Properly documented, including versionadded, versionchanged as needed.

[Julian-O]

There were two locations in the code I didn't touch.

kivy/lib/vidcore_lite/egl.pyx defines an Initialise() function (which calls an initialize function).

kivy\modules\_webdebugger includes some JavaScript that checks for a value called "colour". I don't understand the code to know if that is right or wrong, so I assume it is right.

[misl6]

LGTM. Thank you!