Fix 'variable only defined' doctest warnings

Author: Matthias Koeppe

src/sage/misc/c3_controlled.pyx

@@ -1100,7 +1100,7 @@ class HierarchyElement(object, metaclass=ClasscallMetaclass):
         """
         EXAMPLES::
 
-            sage: # needs sage.combinat sage.graphs
+            sage: # needs sage.graphs
             sage: from sage.misc.c3_controlled import HierarchyElement
             sage: P = Poset((divisors(30), lambda x, y: y.divides(x)), facade=True)
             sage: x = HierarchyElement(10, P)

src/sage/repl/interpreter.py

@@ -554,10 +554,10 @@ def preparse_imports_from_sage(self, line):
         Since :trac:`28439`, this also works with more complicated expressions
         containing nested parentheses::
 
-            sage: # needs sage.libs.gap
-            sage: shell = interface_shell_embed(gap)                                    # needs sage.symbolic
+            sage: # needs sage.libs.gap sage.symbolic
+            sage: shell = interface_shell_embed(gap)
             sage: shell.user_ns = locals()
-            sage: ift = InterfaceShellTransformer(shell=shell, config=shell.config,     # needs sage.symbolic
+            sage: ift = InterfaceShellTransformer(shell=shell, config=shell.config,
             ....:     prefilter_manager=shell.prefilter_manager)
             sage: line = '2 + sage((1+2)*gap(-(5-3)^2).sage()) - gap(1+(2-1))'
             sage: line = ift.preparse_imports_from_sage(line)