docs: reflect current state of pyhton config (#23)

Since uv/pip-compile support is now more complete, the readme needs some
tweaks.

---------

Co-authored-by: Adriane Boyd <[email protected]>

Author: karfau

README.md

@@ -198,7 +198,7 @@ A very common thing is to add [`:autoMergePatch`](https://docs.renovatebot.com/p
 ### python
 
 **There is currently only [limited / "alpha level" support](https://github.com/renovatebot/renovate/blob/main/lib/modules/manager/pip-compile/readme.md) for python using `pip-compile`.
-This configuration has not been used with python projects for a while, it most certainly needs changes.**
+This configuration is currently only used in a small number of python projects, so it may need modifications. You can test it in [bettermarks/renovate-config-test-pip-compile](https://github.com/bettermarks/renovate-config-test-pip-compile) by modifying the dependency files and the renovate config in order to see what updates renovate produces.**
 
 ```json
 {
@@ -211,11 +211,17 @@ It includes the following presets:
 
 - the [default config](#default) from this repository
 
-
 and it configures the following:
 
-- constraints python to 3.6
-- Enables [pip-compile](https://docs.renovatebot.com/modules/manager/pip-compile/) manager (and disables [pip_requirements](https://docs.renovatebot.com/modules/manager/pip_requirements/) and [pip_setup](https://docs.renovatebot.com/modules/manager/pip_setup/) managers since they seem to be conflicting?)
+- Enables [pip-compile](https://docs.renovatebot.com/modules/manager/pip-compile/) manager (and disables [pip_requirements](https://docs.renovatebot.com/modules/manager/pip_requirements/) and [pip_setup](https://docs.renovatebot.com/modules/manager/pip_setup/) managers since we don't use those)
+
+If you found a config that works for you, please consider updating this one after testing it in [bettermarks/renovate-config-test-pip-compile](https://github.com/bettermarks/renovate-config-test-pip-compile).
 
 **you can override all of this per repo!**
-if you found a config that works for you, please consider to update this one.
+
+It is very likely (especially for `uv pip compile`, which doesn't include the python version in the header) that you want to specify the python version in the config:
+```
+  "constraints": {
+    "python": "==3.9" 
+  },
+```