patch 8.2.0314: short name not set for terminal buffer

Problem:    Short name not set for terminal buffer.
Solution:   Set the short name. (closes #5687)
diff --git a/src/terminal.c b/src/terminal.c
index 10bfae8..342275e 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -566,6 +566,8 @@
 	    }
 	}
     }
+    vim_free(curbuf->b_sfname);
+    curbuf->b_sfname = vim_strsave(curbuf->b_ffname);
     curbuf->b_fname = curbuf->b_ffname;
 
     if (opt->jo_term_opencmd != NULL)