Update pandas requirement from <1.6 to <2.1

Updates the requirements on [pandas](https://github.com/pandas-dev/pandas) to permit the latest version.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Changelog](https://github.com/pandas-dev/pandas/blob/main/RELEASE.md)
- [Commits](pandas-dev/pandas@0.3.0...v2.0.0)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -78,7 +78,7 @@ dependencies = [
   "influxdb",
   "influxdb-client[ciso]",
   "paho-mqtt",
-  "pandas<1.6",
+  "pandas<2.1",
   "streamz",
   "toolz",
   "yarl<2",