Jsonrpc: don't bind inhibit-read-only to t so early

Jsonrpc: don't bind inhibit-read-only to t so early

Related to https://github.com/joaotavora/eglot/discussions/1202, where
because of this very wide binding to inhibit-read-only to t, Eglot was
managing to write into read-only buffers from the response handlers
that ran from within the stack of the jsonrpc.el process filter.

This is of course illegal and dangerous, but Eglot wasn't made aware
because of the binding.

* lisp/jsonrpc.el (jsonrpc--process-filter): Don't bind
inhibit-read-only so early.