Bump version to 1.20.6

Updated version number from 1.20.5 to 1.20.6 in pyproject.toml.

Author: ss0832

pyproject.toml

@@ -11,7 +11,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "MultiOptPy"
-version = "1.20.5"
+version = "1.20.6"
 description = "Multifunctional geometry optimization tools for quantum chemical calculations."
 readme = "README.md"
 requires-python = ">=3.12"
@@ -47,3 +47,4 @@ orientsearch = "multioptpy.entrypoints:run_orientsearch"
 where = ["."]
 
 include = ["multioptpy*"]
+