chore(deps): update dependency flask to v3

Author: renovate[bot]

requirements.txt

@@ -1,7 +1,7 @@
 click<8.2.0, >=8.1.3
 cloudinary>=1.34.0, <1.35.0
 flake8>=3.8.4, <3.9.0
-Flask>=2.3.3, <2.4.0
+Flask>=3.0.0, <3.1.0
 Flask-GFM>=0.1.1, <0.2.0
 Flask-Markdown>=0.3, <0.4.0
 Flask-SQLAlchemy>=3.0.3, <3.1.0