gnutls: fix build with --disable-verbose

gnutls: fix build with --disable-verbose

infof() parameters must be defined event with --disable-verbose since
commit dac293cfb702 ("lib: apache style infof and trace
macros/functions").

Move also 'ptr' definition under !CURL_DISABLE_VERBOSE_STRINGS.

Fixes the following build failure:

In file included from ../lib/sendf.h:29,
                 from vtls/gtls.c:44:
vtls/gtls.c: In function 'Curl_gtls_verifyserver':
vtls/gtls.c:841:34: error: 'version' undeclared (first use in this function); did you mean 'session'?
  841 |         gnutls_protocol_get_name(version), ptr);
      |                                  ^~~~~~~

Closes #12505