Typo: "symbols characters" should be "symbol characters".

More precisely, we should speak of chars that have have symbol syntax.

For many users "symbol characters" won't necessarily be understood.

In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)

of 2019-08-29

Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd

Windowing system distributor `Microsoft Corp.', version 10.0.19043

Configured using:

`configure --without-dbus --host=x86_64-w64-mingw32

--without-compress-install 'CFLAGS=-O2 -static -g3''