runtime: remove useless empty string literal
runtime: remove useless empty string literal

Assumingly this appears to have been a bug in c2go, as this appeared in
https://go.dev/cl/172260043.

Change-Id: I8477ec226ffb31268b9c479af13b0fcf401dbeec
Reviewed-on: https://go-review.googlesource.com/c/go/+/418276
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>
Run-TryBot: Michael Pratt <e7f1edc6d5aa9f6c8c377425db8f1a5816cbbb88@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go