Fix typo in Lib/tracepack.py (GH-19605)

Typo fix: "emites" -> "emit".

Author: wudenggang

Lib/traceback.py

@@ -551,7 +551,7 @@ def format_exception_only(self):
         The return value is a generator of strings, each ending in a newline.
 
         Normally, the generator emits a single string; however, for
-        SyntaxError exceptions, it emites several lines that (when
+        SyntaxError exceptions, it emits several lines that (when
         printed) display detailed information about where the syntax
         error occurred.