`koch pdf` produces a warning about unknown substitution 'nimversion'
### Description

When compiling the PDF documentation with `koch pdf` the string `|nimversion|` in the Markdown files is not substituted.

### Nim Version

Nim Compiler Version 2.0.8 [Linux: amd64]
Compiled at 2024-07-03
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: 5935c3bfa9fec6505394867b23510eb5cbab3dbf
active boot switches: -d:release

### Current Output

```text
nim-2.0.8-linux_x64/nim-2.0.8/doc/manual.md(6, 12) Warning: unknown substitution 'nimversion' [UnknownSubstitutionX]
```


### Expected Output

_No response_

### Possible Solution

It seem like the environment variable nimversion does not get correctly passed. Probably, changing the procedure signature `buildPdfDoc*(nimArgs, destPath: string)` to `buildPdfDoc*(args: string, destPath: string)` in `tools/kochdocs.nim` and adding `let args = nimArgs & " " & args` to the body (as in `buildDocsDir`) would fix it.

### Additional Information

_No response_