Consider increasing read-process-output-max

Might improve performance when receiving large JSON objects? Or when receiving them, er, slowly?

```
read-process-output-max is a variable defined in ‘C source code’.

Its value is 4096

Maximum number of bytes to read from subprocess in a single chunk.
Enlarge the value only if the subprocess generates very large (megabytes)
amounts of data in one go.

On GNU/Linux systems, the value should not exceed
/proc/sys/fs/pipe-max-size. See pipe(7) manpage for details.

Probably introduced at or before Emacs version 27.1.

[back]

```