subString should be substring in Handbook

[norm-krumpe]

Issue description

On page 143 of the second edition of the handbook (but first printing?), chapter 11, under "Syntax introduced" the String.substring() function is incorrectly capitalized as String.subString(). It is correct in the rest of that chapter.

URL(s) of affected page(s)

Proposed fix

Change String.subString() to String.substring() in the "Syntax introduced" section of chapter 11.

[REAS]

This is scheduled to be fixed for the fifth printing. Thank you!