update CHANGELOG and bump version to 6.21.4 (#2008)

Author: xrmx

CHANGELOG.asciidoc

@@ -32,6 +32,14 @@ endif::[]
 [[release-notes-6.x]]
 === Python Agent version 6.x
 
+[[release-notes-6.21.4]]
+==== 6.21.4 - 2024-03-19
+
+[float]
+===== Bug fixes
+
+* Fix urllib3 2.0.1+ crash with many args {pull}2002[#2002]
+
 [[release-notes-6.21.3]]
 ==== 6.21.3 - 2024-03-08
 

elasticapm/version.py

@@ -28,5 +28,5 @@
 #  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 #  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-__version__ = (6, 21, 3)
+__version__ = (6, 21, 4)
 VERSION = ".".join(map(str, __version__))