Python 3.6 is EOL

I don't think we should put a minimal requirement which is outdated so prominently. It's also out of sync with the spec in the project metadata which specifies 3.8. Let's try to keep the project metadata itself up to date. https://github.com/opengisch/qfieldcloud-sdk-python/blob/master/pyproject.toml#L11

documentation/reference/qfieldcloud/sdk.en.md

@@ -5,9 +5,6 @@ tx_slug: documentation_reference_qfieldcloud_sdk
 
 `qfieldcloud-sdk` is the official client to connect to [QFieldCloud API](api.md) either as a python module, or directly from the command line.
 
-!!! note
-    `qfieldcloud-sdk` requires Python >=3.6
-
 ## Install
 
 `pip install qfieldcloud-sdk`