fix(frontends/lean/parser): remove unnecessary '#' after error

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/frontends/lean/parser.cpp

@@ -2005,6 +2005,8 @@ public:
                     show_prompt();
                     while (curr() != scanner::token::CommandId && curr() != scanner::token::Eof && curr() != scanner::token::Period)
                         next();
+                    if (curr_is_period())
+                        next();
                 });
         }
         return !m_found_errors;

tests/lean/interactive/t2.lean.expected.out

@@ -14,7 +14,7 @@ H : a, a : Bool, b : Bool ⊢ b ⇒ a ∧ b
 ## Proof state:
 H::1 : b, H : a, a : Bool, b : Bool ⊢ a ∧ b
 ## Error (line: 9, pos: 5) failed to prove theorem, proof has been aborted
-# #   Assumed: a
+#   Assumed: a
   Assumed: b
 # Variable a : Bool
 Variable b : Bool

tests/lean/interactive/t4.lean

@@ -0,0 +1,2 @@
+Theorem (a : Bool) : a.
+Echo "done".

tests/lean/interactive/t4.lean.expected.out

@@ -0,0 +1,6 @@
+Type Ctrl-D or 'Exit.' to exit or 'Help.' for help.
+#   Set: pp::colors
+  Set: pp::unicode
+Error (line: 4, pos: 8) invalid definition, identifier expected
+# done
+#