remove escaping of quotes

[frrad]

According to https://www.gnu.org/software/gawk/manual/html_node/Escape-Sequences.html the " need only be escaped as \" in string constants.

I suspect from googling (though cannot confirm) that in gawk 5.0+ this escaping causes a warning.

I have also checked that this PR causes no regression in the existing tests.

@jagarsoft Can you confirm that this patch fixes your problem on gawk 5?