deps(book): update matplotlib requirement from >=3.7.0 to >=3.9.4

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@v3.9.0...v3.9.4)

---
updated-dependencies:
- dependency-name: matplotlib
  dependency-version: 3.9.4
  dependency-type: direct:production
...

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

Author: dependabot[bot]

binder/requirements.txt

@@ -20,7 +20,7 @@ ipykernel>=6.31.0
 ipywidgets>=8.0.0
 
 # Visualization (for milestone examples and modules)
-matplotlib>=3.9.0
+matplotlib>=3.9.4
 
 # Type checking support
 typing-extensions>=4.12.0

book/tools/dependencies/requirements.txt

@@ -14,7 +14,7 @@ pandas>=2.0.0
 titlecase>=2.4.1
 rich>=13.0.0
 numpy>=1.24.0
-matplotlib>=3.7.0
+matplotlib>=3.9.4
 
 # --- Additional Production & Tooling Dependencies ---
 nltk>=3.8