Fix markdown syntax in "Mark API as experimental"

tecosaur · tecosaur · commit af972e0a7720 · 2024-09-20T22:33:07.000+08:00
Four spaces are needed in admonitions, not two. Amends 8332e45.
diff --git a/docs/src/index.md b/docs/src/index.md
@@ -1,8 +1,8 @@
 # [StyledStrings](@id stdlib-styledstrings)
 
 !!! note
-  The API for StyledStrings and AnnotatedStrings is considered experimental and is subject to change between
-  Julia versions.
+    The API for StyledStrings and AnnotatedStrings is considered experimental and is subject to change between
+    Julia versions.
 
 ## [Styling](@id stdlib-styledstrings-styling)
 
