doc: unpin version of myst-parser

The regression in `myst-parser` has been fixed, so we can use the
latest version again.

Signed-off-by: Ruth Fuchss <ruth.fuchss@canonical.com>

doc/.sphinx/build_requirements.py

@@ -103,7 +103,7 @@ def DeduplicateExtensions(extensionNames: [str]):
         requirements.append("sphinxext-opengraph")
 
     if IsMyStParserUsed():
-        requirements.append("myst-parser==2.0.0")
+        requirements.append("myst-parser")
         requirements.append("linkify-it-py")
 
     # removes duplicate entries