script/update-docs: use ISO-8601 dates for history

The script script/update-git-version.rb already uses ISO-8601 dates,
which are less confusing for most people.

Update script/update-docs.rb to use ISO-8601 date format too.

Signed-off-by: Toon Claes <toon@iotcl.com>

Author: To1ne

script/update-docs.rb

@@ -322,7 +322,7 @@ def index_doc(filter_tags, doc_list, get_content)
     version_data["commit_sha"] = commit_sha
     version_data["tree_sha"] = tree_sha
     version_data["committed"] = ts
-    version_data["date"] = ts.strftime("%m/%d/%y")
+    version_data["date"] = ts.strftime("%Y-%m-%d")
 
     ext = Version.version_to_num(version) < 2_490_000 ? 'txt' : 'adoc'
     tag_files = doc_list.call(tree_sha)