patch 8.0.1492: memory leak in balloon_split()

Problem:    Memory leak in balloon_split().
Solution:   Free the balloon lines. Free the balloon when exiting.
diff --git a/src/misc2.c b/src/misc2.c
index 368303e..0deccdf 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -1116,6 +1116,10 @@
     spell_free_all();
 # endif
 
+#if defined(FEAT_INS_EXPAND) && defined(FEAT_BEVAL_TERM)
+    ui_remove_balloon();
+# endif
+
 # if defined(FEAT_USR_CMDS)
     /* Clear user commands (before deleting buffers). */
     ex_comclear(NULL);