runtime: update the variable name in comment
runtime: update the variable name in comment

The comment use allg to refer to allgs in code. Update the comment to
use the same variable name.

Change-Id: Id059fce7846776737fb038b86bcf8765a4a7c9c0
GitHub-Last-Rev: 234fb0a208f105352d33456159725a3fce3a3071
GitHub-Pull-Request: golang/go#46723
Reviewed-on: https://go-review.googlesource.com/c/go/+/327629
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Trust: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,golang/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,CAFxX/go,golang/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,cloudflare/go,CAFxX/go,golang/go,cloudflare/go,golang/go,CAFxX/go,cloudflare/go,nawawi/go,nawawi/go,golang/go,CAFxX/go,golang/go,nawawi/go,cloudflare/go,cloudflare/go