Bring Expressions subchapters up to the quality standard

[Havvy]

• [ ] Literal expressions
• [ ] Path expressions
• [ ] Block expressions
• [ ] Operator expressions
• [ ] Grouped expressions
• [ ] Array and index expressions
• [x] Tuple and index expressions
• [ ] Struct expressions
• [ ] Enum variant expressions
• [ ] Call expressions
• [ ] Method call expressions
• [ ] Field access expressions
• [ ] Closure expressions
• [ ] Loop expressions
• [ ] Range expressions
• [ ] If and if let expressions
• [ ] Match expressions
• [ ] Return expressions
• [ ] Await expressions

Check each expression page and make sure that they are of the quality we are looking for.

[Havvy]

I'm unchecking tuple expressions since I no longer believe they are currently at the quality needed. That said, I'm currently working on that page. It was originally checked when the list was created.

[Havvy]

Checking tuples back off with #990 merged.