fix: fix sslmode typo

[mschoettle]

We are trying to use SSL with MariaDB and ran into the issue with ssl_mode (fixed by the recently merged #475). We tried installing the latest commit on main and it produces the following error when building:

running build_ext
      building 'MySQLdb._mysql' extension
      creating build/temp.linux-aarch64-cpython-310
      creating build/temp.linux-aarch64-cpython-310/src
      creating build/temp.linux-aarch64-cpython-310/src/MySQLdb
      gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC "-Dversion_info=(2, 2, 0, 'dev', 0)" -D__version__=2.2.0.dev0 -I/usr/local/include/python3.10 -c src/MySQLdb/_mysql.c -o build/temp.linux-aarch64-cpython-310/src/MySQLdb/_mysql.o -I/usr/include/mariadb/ -std=c99
      In file included from /usr/local/include/python3.10/Python.h:8,
                       from src/MySQLdb/_mysql.c:46:
      /usr/local/include/python3.10/pyconfig.h:1643: warning: "_POSIX_C_SOURCE" redefined
       1643 | #define _POSIX_C_SOURCE 200809L
            |
      In file included from /usr/include/aarch64-linux-gnu/sys/types.h:25,
                       from /usr/include/mariadb/mysql.h:38,
                       from src/MySQLdb/_mysql.c:29:
      /usr/include/features.h:310: note: this is the location of the previous definition
        310 | # define _POSIX_C_SOURCE 199506L
            |
      src/MySQLdb/_mysql.c: In function ‘_mysql_ConnectionObject_Initialize’:
      src/MySQLdb/_mysql.c:534:13: error: ‘sslmode_num’ undeclared (first use in this function); did you mean ‘ssl_mode_num’?
        534 |         if (sslmode_num >= SSLMODE_REQUIRED) {
            |             ^~~~~~~~~~~
            |             ssl_mode_num
      src/MySQLdb/_mysql.c:534:13: note: each undeclared identifier is reported only once for each function it appears in
      src/MySQLdb/_mysql.c:535:81: error: ‘enforce_tls’ undeclared (first use in this function)
        535 |             mysql_optionsv(&(self->connection), MYSQL_OPT_SSL_ENFORCE, (void *)&enforce_tls);
            |                                                                                 ^~~~~~~~~~~
      error: command '/usr/bin/gcc' failed with exit code 1
      [end of output]

This PR fixes the sslmode typo and replaces enforce_tls with 1.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (ba85984) 88.86% compared to head (8def204) 88.86%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #609   +/-   ##
=======================================
  Coverage   88.86%   88.86%           
=======================================
  Files           7        7           
  Lines         548      548           
=======================================
  Hits          487      487           
  Misses         61       61           

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[methane]

Thank you. We need CI that uses mariadbclient.