Edit cursor.prev() method docs in lexer
Edit cursor.prev() method docs in lexer

Fix missing punctuation

graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust