cmd/go: fix long test builders

CL 343732 enabled -G=3 by default. The types2 typechecker uses slighly
different error message format for language feature constraint.

The old typechecker format:

	vendor/example.net/need117/need117.go:5:16: cannot convert s (type []byte) to type *[4]byte:
		conversion of slices to array pointers only supported as of -lang=go1.17

The new format:

	vendor/example.net/need117/need117.go:5:17: conversion of slices to array pointers only supported as of -lang=go1.17

caused the long test builders failed.

This CL fixes the test by relaxing the regext pattern a bit, so it can
match both the format.

Change-Id: I1c4acaa9e34b6c08dccbbc3ce7a99d4cd79f748a
Reviewed-on: https://go-review.googlesource.com/c/go/+/344212
Trust: Cuong Manh Le <[email protected]>
Trust: Robert Griesemer <[email protected]>
Run-TryBot: Cuong Manh Le <[email protected]>
Run-TryBot: Robert Griesemer <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>

Author: cuonglm

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

@@ -26,7 +26,7 @@ go mod vendor
 
 ! grep 1.17 vendor/modules.txt
 ! go build example.net/need117
-stderr '^vendor[/\\]example\.net[/\\]need117[/\\]need117.go:5:18: .*\n\tconversion of slices to array pointers only supported as of -lang=go1\.17'
+stderr '^vendor[/\\]example\.net[/\\]need117[/\\]need117.go:5:1[89]: .*conversion of slices to array pointers only supported as of -lang=go1\.17'
 
 ! grep 1.13 vendor/modules.txt
 go build example.net/bad114