Fix assorted spelling mistakes (#7507)

plugins/inputs/mailchimp/chimp_api.go

@@ -178,7 +178,7 @@ type Report struct {
 	Unsubscribed  int    `json:"unsubscribed"`
 	SendTime      string `json:"send_time"`
 
-	TimeSeries    []TimeSerie
+	TimeSeries    []TimeSeries
 	Bounces       Bounces       `json:"bounces"`
 	Forwards      Forwards      `json:"forwards"`
 	Opens         Opens         `json:"opens"`
@@ -237,7 +237,7 @@ type ListStats struct {
 	ClickRate float64 `json:"click_rate"`
 }
 
-type TimeSerie struct {
+type TimeSeries struct {
 	TimeStamp       string `json:"timestamp"`
 	EmailsSent      int    `json:"emails_sent"`
 	UniqueOpens     int    `json:"unique_opens"`