clojure-fill-paragraph won't break lines at the space in `word :word`

I noticed a, to me, weird behavior of `clojure-fill-paragraph`. I was listing keyword arguments in a docstrsing, and when I tried to fill it I ended up with something similar to the screenshot below. I tracked it down to the extra stuff that it is adding to `paragraph-start`, i.e. this code:
```
(let ((paragraph-start
(concat paragraph-start
"\\|\\s-*\\([(:\"[]\\|~@\\|`(\\|#'(\\)"))
```
I don't understand why the regexp is like that, but I don't like the current result.

## Expected behavior

`clojure-fill-paragraph` can break lines at the space in `word :word`.

## Actual behavior


## Steps to reproduce the problem

Try to fill the docstring in
```
(defn some-function
"word word word word word word word word word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word :word word word word word word word word word word word word word word word word word word word word word word word word"
[])
```
## Environment & Version information

### clojure-mode version 5.13

Search for the clojure-fill-paragraph entry point and the paragraph-start customization shown in the issue. Reproduce the documented Clojure function example, then verify that filling can break at the space in `word :word` without regressing the other listed delimiters.

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