runtime: "traceback: unexpected SPWRITE function runtime.systemstack" [1.21 backport]

[gopherbot]

@prattmic requested issue #64934 to be considered for backport to the next 1.21 minor release.

@gopherbot please backport to 1.21. This fixes a regression in a previous backport (#62464).

[gopherbot]

Change https://go.dev/cl/553476 mentions this issue: [release-branch.go1.21] runtime: don't print "unexpected SPWRITE" when printing traceback

[mdempsky]

Approved for backport.

[gopherbot]

Closed by merging caafb50 to release-branch.go1.21.