patch 8.1.2291: memory leak when executing command in a terminal

Problem:    Memory leak when executing command in a terminal.
Solution:   Free "argv". (Dominique Pelle, closes #5208)
diff --git a/src/terminal.c b/src/terminal.c
index a3ca993..dcb4c39 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -844,6 +844,7 @@
 	// :term ++shell command
 	if (unix_build_argv(cmd, &argv, &tofree1, &tofree2) == OK)
 	    term_start(NULL, argv, &opt, eap->forceit ? TERM_START_FORCEIT : 0);
+	vim_free(argv);
 	vim_free(tofree1);
 	vim_free(tofree2);
 	goto theend;