Update MethodInvocations.rst

[erzemmi]

changed grammar from "If no value is provided inside the parentheses, the split method chops up the list whenever it encounters and whitespace (a space, a tab, or a newline)" to "If no value is provided inside the parentheses, the split method chops up the list whenever it encounters a whitespace (a space, a tab, or a newline)."

The "and" before "whitespace" was incorrect and made the sentence confusing.

[presnick]

Merged to a different branch. Thanks.