chore: update python version

Author: brenorb

pyproject.toml

@@ -7,7 +7,7 @@ name = "bdkpython"
 version = "2.1.0.dev0"
 description = "The Python language bindings for the Bitcoin Development Kit"
 readme = "README.md"
-requires-python = ">=3.7"
+requires-python = ">=3.9"
 license = "MIT OR Apache-2.0"
 license-files = ["LICENSE-MIT", "LICENSE-APACHE"]
 authors = [
@@ -33,4 +33,4 @@ where = ["src"]
 bdkpython = ["libbdkffi.*"]
 
 [tool.pytest.ini_options]
-pythonpath = ["."]
+pythonpath = ["."]