patch 8.2.3197: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move a few more error messages to errors.h.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 1efefb1..c1d0295 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2112,7 +2112,7 @@
 	if (sandbox != 0 && !(ea.argt & EX_SBOXOK))
 	{
 	    // Command not allowed in sandbox.
-	    errormsg = _(e_sandbox);
+	    errormsg = _(e_not_allowed_in_sandbox);
 	    goto doend;
 	}
 #endif