requirements: update matplotlib requirement from <3.7.6 to <3.9.3

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@v0.91.2...v3.9.2)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -6,7 +6,7 @@ graphviz<0.21.0
 grpcio<1.67.0
 leabra-psyneulink<0.3.3
 llvmlite<0.44
-matplotlib<3.7.6
+matplotlib<3.9.3
 modeci_mdf<0.5, >=0.4.3; (platform_machine == 'AMD64' or platform_machine == 'x86_64' or platform_machine == 'arm64' or platform_machine == 'aarch64') and platform_python_implementation == 'CPython' and implementation_name == 'cpython'
 networkx<3.4
 numpy>=1.21.0, <1.26.5

tutorial_requirements.txt

@@ -1,3 +1,3 @@
 graphviz<0.21.0
 jupyter<1.0.1
-matplotlib<3.7.6
+matplotlib<3.9.3