Clarify decode_unicode behaviour in iter_{content,lines} docstrings (#7365)

Author: cjriches

src/requests/models.py

@@ -811,8 +811,10 @@ def iter_content(self, chunk_size=1, decode_unicode=False):
         chunks are received. If stream=False, data is returned as
         a single chunk.
 
-        If decode_unicode is True, content will be decoded using the best
-        available encoding based on the response.
+        If decode_unicode is True, content will be decoded using encoding
+        information from the response. If no encoding information is available,
+        bytes will be returned. This can be bypassed by manually setting
+        `encoding` on the response.
         """
 
         def generate():
@@ -863,6 +865,9 @@ def iter_lines(
         stream=True is set on the request, this avoids reading the
         content at once into memory for large responses.
 
+        The decode_unicode param works the same as in `iter_content`, with the
+        same caveats.
+
         .. note:: This method is not reentrant safe.
         """