[lldb][man][nfc] Don't register a markdown parser when building man packages (#98420)

This reduces Sphinx dependencies for building lldb man pages as lldb man
pages don't use markdown.

Author: alanzhao1

lldb/docs/conf.py

@@ -64,6 +64,11 @@
 
 autodoc_default_options = {"special-members": True}
 
+# The suffix of source filenames.
+source_suffix = {
+    ".rst": "restructuredtext",
+}
+
 # Unless we only generate the basic manpage we need the plugin for generating
 # the Python API documentation.
 if not building_man_page:
@@ -83,15 +88,13 @@
     # a list of builtin themes.
     html_theme = "furo"
 
+    # Since man pages do not use markdown, we do not need to register a markdown
+    # parser.
+    source_suffix[".md"] = "markdown"
+
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ["_templates"]
 
-# The suffix of source filenames.
-source_suffix = {
-    ".rst": "restructuredtext",
-    ".md": "markdown",
-}
-
 # The encoding of source files.
 # source_encoding = 'utf-8-sig'