testdata: adjust for newer Go 1.18 tip version

The output of "go version -m" has changed format slightly:

	main: devel go1.18-b357b05b70 Thu Dec 23 20:03:38 2021 +0000
		path	test/main
		mod	test/main	(devel)
		build	-compiler=gc
		build	-tags=veryuniquebuildtag
		build	CGO_ENABLED=1
		build	CGO_CFLAGS=
		build	CGO_CPPFLAGS=
		build	CGO_CXXFLAGS=
		build	CGO_LDFLAGS=
		build	GOARCH=amd64
		build	GOOS=linux
		build	GOAMD64=v3
		build	vcs=git
		build	vcs.revision=5c92c49896a08d9152669b5bcbf0a9d85c5cb2ed
		build	vcs.time=2021-12-24T18:52:32Z
		build	vcs.modified=true

testdata/scripts/modinfo.txt

@@ -24,8 +24,8 @@ go build -tags veryuniquebuildtag
 go version -m main$exe
 stdout 'path\s*test/main'
 stdout 'mod\s*test/main\s*\(devel\)'
-[go1.18] stdout 'build\s*tags.*veryuniquebuildtag'
-[go1.18] stdout 'build\s*gitrevision.*'${HEAD_COMMIT_SHA}
+[go1.18] stdout 'build\s*-tags=veryuniquebuildtag'
+[go1.18] stdout 'build\s*vcs.revision='${HEAD_COMMIT_SHA}
 
 -- go.mod --
 module test/main