Bump azure-core from 1.25.1 to 1.26.0 in /demo/graphtutorial

Bumps [azure-core](https://github.com/Azure/azure-sdk-for-python) from 1.25.1 to 1.26.0.
- [Release notes](https://github.com/Azure/azure-sdk-for-python/releases)
- [Commits](Azure/azure-sdk-for-python@azure-core_1.25.1...azure-core_1.26.0)

---
updated-dependencies:
- dependency-name: azure-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

demo/graphtutorial/requirements.txt

@@ -1,4 +1,4 @@
-azure-core==1.25.1
+azure-core==1.26.0
 azure-identity==1.11.0
 certifi==2022.9.24
 cffi==1.15.1