runtime: add missing closing curly brace in runtime corruption error message

runtime: add missing closing curly brace in runtime corruption error message

(Fixing the most important part of this bug.)

Updates #56426

Change-Id: If657ae47a5fe7dacc31d2c487e53e9f2dd5d03bf
Reviewed-on: https://go-review.googlesource.com/c/go/+/445695
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Auto-Submit: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>