bug#40180: 27.0.90; cl-concatenate returns wrong result

[Joost Kremers]

`cl-concatenate` seems to return the wrong result:

```
ELISP> (cl-concatenate 'list '(a b c) '(d e f))
((a b c) 
(d e f))
```

In Emacs 26 the return value was `(a b c d e f)`, which I assume 
should still be the return value in Emacs 27, given that Common 
Lisp hasn't changed. :-)



In GNU Emacs 27.0.90 (build 2, x86_64-pc-linux-gnu, GTK+ Version 
3.22.30)
of 2020-03-11 built on IdeaPad
Repository revision: 1bc3fa0bd02cb167ae82b65fc56f95651d2bea16
Repository branch: emacs-27
Windowing system distributor 'The X.Org Foundation', version 
11.0.11906000
System Description: elementary OS 5.1.2 Hera

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--
Joost Kremers
Life has its moments