go/packages: change ParserError to ParseError
go/packages: change ParserError to ParseError

Correct minor typo from
https://go-review.googlesource.com/c/tools/+/139317/3.

Change-Id: I76b661fbe136914b903011990e48c74563115ae6
Reviewed-on: https://go-review.googlesource.com/139318
Reviewed-by: Michael Matloob <4562438b12c14e81a47550acde616ff328a909f8@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools