[temp.deduct.general] Lambda SFINAE examples are incorrect

[t3nsor]

Full name of submitter: Brian Bi

Issue description: The third and fourth comments in Example 7 in [temp.deduct.general] incorrectly treat the lambda-introducer and trailing return type of a lambda as if they're part of the lambda body.

Suggested resolution:: Amend the third comment to // calls h(...) and the fourth to // calls i(...). Then, for consistency, remove the comments // #1 and // #2 and amend the final comment to // calls j(...).