Update matplotlib requirement from ==3.9.* to ==3.10.* in /server

Updates the requirements on [matplotlib](https://github.com/matplotlib/matplotlib) to permit the latest version.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.9.0rc1...v3.10.0)

---
updated-dependencies:
- dependency-name: matplotlib
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

server/requirements.txt

@@ -15,7 +15,7 @@ djangorestframework==3.15.*
 emoji==2.14.*
 icalendar==6.1.*
 lxml==5.3.*
-matplotlib==3.9.*
+matplotlib==3.10.*
 numpy==2.2.*
 orjson==3.10.*
 openpyxl~=3.1.4