refactor: remove redundant err declarations (#32381)

(cherry picked from commit f4d3aaeeb9e1b11c5495e4608a3f52f316c35758)

Conflicts:
	- modules/charset/charset_test.go
	  Resolved by manually changing a `=` to `:=`, as per the
	  original patch. Conflict was due to `require.NoError`.

build/generate-emoji.go

@@ -53,8 +53,6 @@ func (e Emoji) MarshalJSON() ([]byte, error) {
 }
 
 func main() {
-	var err error
-
 	flag.Parse()
 
 	// generate data
@@ -83,8 +81,6 @@ var replacer = strings.NewReplacer(
 var emojiRE = regexp.MustCompile(`\{Emoji:"([^"]*)"`)
 
 func generate() ([]byte, error) {
-	var err error
-
 	// load gemoji data
 	res, err := http.Get(gemojiURL)
 	if err != nil {