Bump redis from 6.2.0 to 6.4.0 in /demos (#1594)

Bumps [redis](https://github.com/redis/redis-py) from 6.2.0 to 6.4.0.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v6.2.0...v6.4.0)

---
updated-dependencies:
- dependency-name: redis
  dependency-version: 6.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

demos/blog/requirements.txt

@@ -4,7 +4,7 @@ aiohttp-security[session]==0.5.0
 asyncpg==0.30.0
 bcrypt==4.3.0
 pytoml==0.1.21
-redis==6.2.0
+redis==6.4.0
 SQLalchemy==2.0.41
 
 # testing

demos/graphql-demo/requirements-dev.txt

@@ -8,7 +8,7 @@ graphene==2.1.9
 graphql-core==2.3.2
 graphql-ws==0.4.4
 psycopg2-binary==2.9.10
-redis==6.2.0
+redis==6.4.0
 
 mypy==1.16.1
 flake8==7.3.0

demos/shortify/requirements.txt

@@ -1,7 +1,7 @@
 aiohttp==3.12.15
 aiohttp-jinja2==1.6
 pyyaml==6.0.2
-redis==6.2.0
+redis==6.4.0
 trafaret==2.1.1
 pytest-aiohttp==1.1.0
 pytest-asyncio==0.26