encoding/json/v2: fix typo in documentation about errors.AsType
CL 708495 mass migrated the stdlib to use errors.AsType.
It rewrote the documentation, but uses the non-pointer type
of SemanticError or SyntacticError, which is invalid since
the Error method is declared on the pointer receiver.
Also, call errors.AsType on a separate line for readability.
Change-Id: I2eaf59614e2b58aa4bc8669ab81ce64168c54f13
Reviewed-on: https://go-review.googlesource.com/c/go/+/714660 Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
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