Revert "Last 0.20.x release: update dependencies to use specific versions for guidata and PlotPy"

This reverts commit 327aaed.

Author: PierreRaybaut

pyproject.toml

@@ -40,8 +40,8 @@ classifiers = [
 ]
 requires-python = ">=3.9, <4"
 dependencies = [
-    "guidata == 3.9.0",
-    "PlotPy == 2.7.5",
+    "guidata >= 3.9",
+    "PlotPy >= 2.7.5",
     "SciPy >= 1.5",
     "scikit-image >= 0.18",
     "pandas >= 1.2",