doc: Update comments about file types in _types.py (#1898)

* doc: Update comments about file types in _types.py

#1897

* Update httpx/_types.py

Co-authored-by: Tom Christie <tom@tomchristie.com>

Author: adriangb

httpx/_types.py

@@ -83,11 +83,11 @@
 
 FileContent = Union[IO[bytes], bytes]
 FileTypes = Union[
-    # file (or text)
+    # file (or bytes)
     FileContent,
-    # (filename, file (or text))
+    # (filename, file (or bytes))
     Tuple[Optional[str], FileContent],
-    # (filename, file (or text), content_type)
+    # (filename, file (or bytes), content_type)
     Tuple[Optional[str], FileContent, Optional[str]],
 ]
 RequestFiles = Union[Mapping[str, FileTypes], Sequence[Tuple[str, FileTypes]]]