apacheGH-38240: [Docs] version_match should match the version from ve…

…rsions.json (apache#38241)

This PR corrects the version for the `version_match` to be equal to the version defined in versions.json. This way the text is correctly displayed in the version switcher button.
* Closes: apache#38240

Authored-by: AlenkaF <frim.alenka@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>

docs/source/conf.py

@@ -288,6 +288,14 @@
 # documentation.
 #
 
+switcher_version = version
+if ".dev" in version:
+    switcher_version = "dev/"
+else:
+    # If we are not building dev version of the docs, we are building
+    # docs for the stable version
+    switcher_version = ""
+
 html_theme_options = {
     "show_toc_level": 2,
     "use_edit_page_button": True,
@@ -313,7 +321,7 @@
     "show_version_warning_banner": True,
     "switcher": {
         "json_url": "/docs/_static/versions.json",
-        "version_match": version,
+        "version_match": switcher_version,
     },
 }