[Opserty]

If think you can edit the controlpanel.css file in the

/cpstyles/{STYLE_NAME}/

folder (where the style name is the admin style you are using).

Make a back up of the file first and then look for this:

/* For those times when you need a monospace font */
.code, .code-g, .code-i, code-c
{
	font: 10pt consolas, 'courier new', courier, monospace;
}

Change it to:

/* For those times when you need a monospace font */
.code, .code-g, .code-i, code-c
{
	font: 10pt  'courier new', courier, monospace;
}

I haven't test it but I think that should solve it.