Update Doc/library/warnings.rst

Co-authored-by: Alyssa Coghlan <ncoghlan@gmail.com>

Author: bebound

Doc/library/warnings.rst

@@ -80,8 +80,9 @@ The following warnings category classes are currently defined:
 |                                  | unless triggered by code in ``__main__``).    |
 +----------------------------------+-----------------------------------------------+
 | :exc:`SyntaxWarning`             | Base category for warnings about dubious      |
-|                                  | syntactic features (emitted when compiling    |
-|                                  | Python source code to bytecode).              |
+|                                  | syntactic features (typically emitted when  |
+|                                  | compiling Python source code, and hence |
+|                                  | may not be suppressed by runtime filters) |
 +----------------------------------+-----------------------------------------------+
 | :exc:`RuntimeWarning`            | Base category for warnings about dubious      |
 |                                  | runtime features.                             |