cmd/go: adjust test script (fix build)

Fixes build failure introduced by CL 791540.

For #63813.

Change-Id: I7808e7c5b5fe694439f921a0d90fbaa994298229
Reviewed-on: https://go-review.googlesource.com/c/go/+/791700
TryBot-Bypass: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/go/testdata/script/godebug_default.txt

diff --git a/src/cmd/go/testdata/script/godebug_default.txt b/src/cmd/go/testdata/script/godebug_default.txt
index 22f8fe6..fdde0c4 100644
--- a/src/cmd/go/testdata/script/godebug_default.txt
+++ b/src/cmd/go/testdata/script/godebug_default.txt
@@ -79,10 +79,10 @@
 # Programs in Go 1.21 work module should trigger run-time error.
 cp go.mod.21 go.mod
 ! go run .
-stderr 'panic: panic called with nil argument'
+stderr 'runtime error: panic called with nil argument'
 
 ! go run rsc.io/panicnil
-stderr 'panic: panic called with nil argument'
+stderr 'runtime error: panic called with nil argument'
 
 # Programs in Go 1.20 work module use old panic nil behavior.
 cp go.mod.20 go.mod
@@ -99,7 +99,7 @@
 
 rm go.mod
 ! go run rsc.io/panicnil@v1.1.0
-stderr 'panic: panic called with nil argument'
+stderr 'runtime error: panic called with nil argument'
 
 -- go.work.21 --
 go 1.21