Remove extraneous word from error message (fixes #1086) (#1087)

Fixes #1086

atproto/data/parse.go

···
 
 func parseFloat(f float64) (int64, error) {
 	if f != float64(int64(f)) {
-		return 0, fmt.Errorf("number was is not a safe integer: %f", f)
+		return 0, fmt.Errorf("number is not a safe integer: %f", f)
 	}
 	return int64(f), nil
 }