Clarify which instance of `upgrade` the reason is referring to

[duianto]

Clarify which instance of upgrade the reason is referring to.

Unwrap/Unwrap/Content/SixtySeconds/creating-basic-closures.json

Lines 36 to 37 in 3a5ee7f

	"answer": "let upgrade() = {\n\tprint(\"Upgrading...\")\n}\nupgrade()",
	"reason": "The parentheses after <code>upgrade<\/code> should not be there.."

The code has two instances of upgrade().
The reason doesn't indicate which one it's referring to.

The first instance is the problem.
It might be helpful to indicate it by adding let before upgrade.

Before:

 "reason": "The parentheses after <code>upgrade<\/code> should not be there.." 

After:

 "reason": "The parentheses after <code>let upgrade<\/code> should not be there.."