src/sage/doctest/sources.py: add "long time" for two tests

Two calls to FileDocTestSource.create_doctests() in this file can take
a while (about 5s) on the first run. This now triggers a "slow
doctest" warning if you are unlucky, and is unusually annoying because
doctesting this file is expected to produce no output in a doctest in
src/sage/doctest/forker.py.

We add "# long time" to correct that random doctest failure. In any
case, the two tests do take a long time.

Author: orlitzky

src/sage/doctest/sources.py

@@ -219,6 +219,7 @@ def _process_doc(self, doctests: list[doctest.DocTest], doc, namespace, start):
 
         EXAMPLES::
 
+            sage: # long time
             sage: from sage.doctest.control import DocTestDefaults
             sage: from sage.doctest.sources import FileDocTestSource
             sage: from sage.doctest.parsing import SageDocTestParser
@@ -931,6 +932,7 @@ def parse_docstring(self, docstring, namespace, start) -> list[doctest.DocTest]:
 
         EXAMPLES::
 
+            sage: # long time
             sage: from sage.doctest.control import DocTestDefaults
             sage: from sage.doctest.sources import FileDocTestSource
             sage: from sage.doctest.parsing import SageDocTestParser