python: Improve docstring highlighting (#31628)

Finn Evers created 

This PR broadens the highlighting for docstrings in Python. 

Previously, only the first docstring for e.g. type aliases was
highlighted in Python files. This happened as only the first occurrence
in the module was considered a docstring. With this change, now all
existing docstrings are actually highlighted as such.

| `main` | This PR | 
| --- | --- |
|
![main](https://github.com/user-attachments/assets/facc96a9-4e98-4063-8b93-d6e9884221ff)
|
![PR](https://github.com/user-attachments/assets/9da557a1-b327-466a-be87-65d6a811e24c)
|

Release Notes:

- Added more docstring highlights for Python.

Change summary

crates/languages/src/python/highlights.scm | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

Detailed changes

crates/languages/src/python/highlights.scm 🔗 

@@ -151,6 +151,12 @@
   "}" @punctuation.special) @embedded
 
 ; Docstrings.
+([
+  (expression_statement (assignment))
+  (type_alias_statement)
+]
+. (expression_statement (string) @string.doc)+)
+
 (module
   .(expression_statement (string) @string.doc)+)
 
@@ -173,13 +179,6 @@
   . (comment) @comment*
   . (expression_statement (string) @string.doc)+)
 
-(module
-  [
-    (expression_statement (assignment))
-    (type_alias_statement)
-  ]
-  . (expression_statement (string) @string.doc)+)
-
 (class_definition
   body: (block
     (expression_statement (assignment))