fix: pkg_resources deprecation, switched to importlib

The _version.py module imported and used the deprecated pkg_resources to retrieve the current version number. It has been replaced with importlib.

src/keycloak/_version.py

@@ -21,6 +21,6 @@
 # IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-import pkg_resources
+from importlib import metadata
 
-__version__ = pkg_resources.get_distribution("python-keycloak").version
+__version__ = metadata.version("python-keycloak")