dispatch: remove stray semicolon (NFC
This cleans up a stray semicolon to allow building with `-Werror=c++98-compat-extra-semi` which is enabled by default in some versions of clang and produces an annoying number of diagnostics when building Swift.
@@ -54,7 +54,7 @@ DISPATCH_ASSUME_NONNULL_BEGIN
* Dispatch sources are used to automatically submit event handler blocks to
* dispatch queues in response to external events.
*/
-DISPATCH_SOURCE_DECL(dispatch_source);
+DISPATCH_SOURCE_DECL(dispatch_source)
__BEGIN_DECLS
