bpo-32452: clarify term 'brackets' in generator tutorial (GH-5079) (#5082)

Updates documentation for generator expressions in classes tutorial: Clarify usage of ambiguous term "brackets" by replacing with "square brackets". Updated subsequent lines to respect line breaks. (GH-5079)
(cherry picked from commit f190eb5)

Author: miss-islington

Doc/tutorial/classes.rst

@@ -873,9 +873,9 @@ Generator Expressions
 =====================
 
 Some simple generators can be coded succinctly as expressions using a syntax
-similar to list comprehensions but with parentheses instead of brackets.  These
-expressions are designed for situations where the generator is used right away
-by an enclosing function.  Generator expressions are more compact but less
+similar to list comprehensions but with parentheses instead of square brackets.
+These expressions are designed for situations where the generator is used right
+away by an enclosing function.  Generator expressions are more compact but less
 versatile than full generator definitions and tend to be more memory friendly
 than equivalent list comprehensions.