fix link to v3 (#5262)

* fix link to v3

we're using the v3 tag instead of stable for readthedocs (stable tag links to a documentation with missing images etc)

* Autofill the version slug

Co-authored-by: Oriol Abril <oriol.abril.pla@gmail.com>

* Remove spaces

* get rid of the button to parse the substitution

* fix link rendering

* add newline at the end of file

Co-authored-by: Michael Osthege <michael.osthege@outlook.com>
Co-authored-by: Oriol Abril <oriol.abril.pla@gmail.com>

Author: 3 people

docs/source/404.md

@@ -28,17 +28,4 @@ do so we have moved some files around and we have
 modified the base url in order to support multi version docs
 (you'll see the version switcher at the bottom right of the page).
 
-::::{grid} 3
-:::{grid-item}
-:::
-:::{grid-item}
-```{button-link} https://docs.pymc.io/en/stable/
-:color: primary
-:expand:
-
-Back to stable version documentation
-```
-:::
-:::{grid-item}
-:::
-::::
+Back to {{ '[documentation homepage](https://docs.pymc.io/en/{}/)'.format(version_slug) }}

docs/source/conf.py

@@ -118,6 +118,10 @@
 # myst and panels config
 jupyter_execute_notebooks = "off"
 myst_enable_extensions = ["colon_fence", "deflist", "dollarmath", "amsmath", "substitution"]
+myst_substitutions = {
+    "version_slug": rtd_version,
+}
+panels_add_bootstrap_css = False
 myst_heading_anchors = None
 
 # The reST default role (used for this markup: `text`) to use for all