minor code style: use `strings.Replace` fourth argument in influxdb (#8225)

Remove 5 lines from the codebase and an unecessary function,
by calling `strings.Replace` with -1 for the fourth argument.

A better alternative to what was merged in #8037

pkg/tsdb/influxdb/query.go

@@ -34,18 +34,13 @@ func (query *Query) Build(queryContext *tsdb.QueryContext) (string, error) {
 		return "", err
 	}
 
-	res = replaceVariable(res, "$timeFilter", query.renderTimeFilter(queryContext))
-	res = replaceVariable(res, "$interval", interval.Text)
-	res = replaceVariable(res, "$__interval_ms", strconv.FormatInt(interval.Value.Nanoseconds()/int64(time.Millisecond), 10))
-	res = replaceVariable(res, "$__interval", interval.Text)
+	res = strings.Replace(res, "$timeFilter", query.renderTimeFilter(queryContext), -1)
+	res = strings.Replace(res, "$interval", interval.Text, -1)
+	res = strings.Replace(res, "$__interval_ms", strconv.FormatInt(interval.Value.Nanoseconds()/int64(time.Millisecond), 10), -1)
+	res = strings.Replace(res, "$__interval", interval.Text, -1)
 	return res, nil
 }
 
-func replaceVariable(str string, variable string, value string) string {
-	count := strings.Count(str, variable)
-	return strings.Replace(str, variable, value, count)
-}
-
 func getDefinedInterval(query *Query, queryContext *tsdb.QueryContext) (*tsdb.Interval, error) {
 	defaultInterval := tsdb.CalculateInterval(queryContext.TimeRange)