patch 8.2.4594: need to write script to a file to be able to source them

Problem:    Need to write script to a file to be able to source them.
Solution:   Make ":source" use lines from the current buffer. (Yegappan
            Lakshmanan et al., closes #9967)
diff --git a/src/vim9script.c b/src/vim9script.c
index 6dce572..870056f 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -71,7 +71,7 @@
     int		    found_noclear = FALSE;
     char_u	    *p;
 
-    if (!getline_equal(eap->getline, eap->cookie, getsourceline))
+    if (!sourcing_a_script(eap))
     {
 	emsg(_(e_vim9script_can_only_be_used_in_script));
 	return;
@@ -633,7 +633,7 @@
     char_u	*cmd_end;
     evalarg_T	evalarg;
 
-    if (!getline_equal(eap->getline, eap->cookie, getsourceline))
+    if (!sourcing_a_script(eap))
     {
 	emsg(_(e_import_can_only_be_used_in_script));
 	return;