Update pyoncat requirement from ~=1.6 to ~=2.1

Updates the requirements on [pyoncat](https://oncat.ornl.gov) to permit the latest version.

---
updated-dependencies:
- dependency-name: pyoncat
  dependency-version: '2.1'
  dependency-type: direct:production
...

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

Author: dependabot[bot]

pyproject.toml

@@ -4,7 +4,7 @@ description = "A desktop application for Lifecycle Managment of data collected f
 dynamic = ["version"]
 requires-python = ">=3.10"
 dependencies = [
-    "pyoncat ~= 1.6"
+    "pyoncat ~= 2.1"
 ]
 readme = "README.md"
 license = { text = "GPL3.0" }