cmd/go: clean up a couple of inconsequential nits in generate

Post-submit glitches caught by reviewers.

LGTM=nightlyone, bradfitz
R=golang-codereviews, nightlyone, bradfitz
CC=golang-codereviews
https://golang.org/cl/126660043

src/cmd/go/generate.go

@@ -161,7 +161,7 @@ type Generator struct {
 // run runs the generators in the current file.
 func (g *Generator) run() (ok bool) {
 	// Processing below here calls g.errorf on failure, which does panic(stop).
-	// If we encouter an error, we abort the package.
+	// If we encounter an error, we abort the package.
 	defer func() {
 		e := recover()
 		if e != nil {

src/cmd/go/generate_test.go

@@ -26,7 +26,6 @@ var splitTests = []splitTest{
 	{"$GOPACKAGE", []string{"sys"}},
 	{"a $XXNOTDEFINEDXX b", []string{"a", "", "b"}},
 	{"/$XXNOTDEFINED/", []string{"//"}},
-	{"$GOARCH", []string{runtime.GOARCH}},
 	{"yacc -o $GOARCH/yacc_$GOFILE", []string{"go", "tool", "yacc", "-o", runtime.GOARCH + "/yacc_proc.go"}},
 }