Removed capitalization for error message (staticcheck)

regex/range2regex.go

@@ -109,7 +109,7 @@ func range2regex(start int, end int) (string, error) {
 		startSlc := intToSlc(rg.start)
 		endSlc := intToSlc(rg.end)
 		if len(startSlc) != len(endSlc) {
-			return "", fmt.Errorf("Error parsing numeric range")
+			return "", fmt.Errorf("error parsing numeric range")
 		}
 		for i := range startSlc {
 			if startSlc[i] == endSlc[i] {