update CHANGELOG and bump version to 5.3.1

===== New Features

* Added support for shortening dicts in local variables {pull}638[#638]

Author: basepi

CHANGELOG.asciidoc

@@ -20,19 +20,24 @@ endif::[]
 
 === Unreleased
 
-https://github.com/elastic/apm-agent-python/compare/v5.3.0\...master[Check the diff]
+https://github.com/elastic/apm-agent-python/compare/v5.3.1\...master[Check the diff]
 
 // Unreleased changes go here
 // When the next release happens, nest these changes under the "Python Agent version 5.x" heading
 
+[[release-notes-5.x]]
+=== Python Agent version 5.x
+
+[[release-notes-5.3.1]]
+==== v5.3.1
+
+https://github.com/elastic/apm-agent-python/compare/v5.3.0\...v5.3.1[Check the diff]
+
 [float]
 ===== New Features
 
 * Added support for shortening dicts in local variables {pull}638[#638]
 
-[[release-notes-5.x]]
-=== Python Agent version 5.x
-
 [[release-notes-5.3.0]]
 ==== v5.3.0
 

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__ = (5, 3, 0)
+__version__ = (5, 3, 1)
 VERSION = ".".join(map(str, __version__))