MkDocs: fix USE_MKDOCS_LATEST feature flag logic (#10515)

* MkDocs: fix `USE_MKDOCS_LATEST` feature flag logic

The logic was inverted and we were installing old MkDocs version to projects
with `USE_MKDOCS_LATEST` feature flag.

Closes #10402

* MkDocs: remove `USE_MKDOCS_LATEST`

This is not required anymore since the logic was inverted and we were installing
always the latest version for old projects, but the old version for new
projects.

It's better to have all of them installing the latest version and call it a day :)

Author: humitos

docs/user/build-default-versions.rst

@@ -41,7 +41,6 @@ Sphinx:
 
 Mkdocs:
   Projects created before April 3, 2019 (April 23, 2019 for :doc:`/commercial/index`) use ``0.17.3``.
-  Projects created before March 9, 2021 use ``1.0.4``.
   New projects use the latest version.
 
 sphinx-rtd-theme:

readthedocs/doc_builder/python_environments.py

@@ -209,12 +209,8 @@ def install_core_requirements(self):
                 self.project.get_feature_value(
                     Feature.DEFAULT_TO_MKDOCS_0_17_3,
                     positive='mkdocs==0.17.3',
-                    negative=self.project.get_feature_value(
-                        Feature.USE_MKDOCS_LATEST,
-                        positive='mkdocs<1.1',
-                        negative='mkdocs',
-                    ),
-                ),
+                    negative="mkdocs",
+                )
             )
         else:
             requirements.extend(

readthedocs/projects/models.py

@@ -1926,7 +1926,6 @@ def add_features(sender, **kwargs):
     DONT_INSTALL_LATEST_PIP = 'dont_install_latest_pip'
     USE_SPHINX_LATEST = 'use_sphinx_latest'
     DEFAULT_TO_MKDOCS_0_17_3 = 'default_to_mkdocs_0_17_3'
-    USE_MKDOCS_LATEST = 'use_mkdocs_latest'
     USE_SPHINX_RTD_EXT_LATEST = 'rtd_sphinx_ext_latest'
 
     # Search related features
@@ -2033,7 +2032,6 @@ def add_features(sender, **kwargs):
             DEFAULT_TO_MKDOCS_0_17_3,
             _("MkDOcs: Install mkdocs 0.17.3 by default"),
         ),
-        (USE_MKDOCS_LATEST, _("MkDocs: Use latest version of MkDocs")),
         (
             USE_SPHINX_RTD_EXT_LATEST,
             _("Sphinx: Use latest version of the Read the Docs Sphinx extension"),