app-emulation/spice-vdagent: remove unused patch

Closes: https://github.com/gentoo/gentoo/pull/8564

app-emulation/spice-vdagent/files/spice-vdagent-0.17.0-add-missing-stub-function.patch

@@ -1,18 +0,0 @@
-Add missing stub function to prevent underlinking error.
-Patch provided by Pat Erley
-See also: https://bugs.gentoo.org/show_bug.cgi?id=585994
-
---- a/src/dummy-session-info.c
-+++ b/src/dummy-session-info.c
-@@ -50,6 +50,11 @@
-     return FALSE;
- }
- 
-+gboolean session_info_session_is_locked(struct session_info *ck)
-+{
-+    return FALSE;
-+}
-+
- gboolean session_info_is_user(struct session_info *si)
- {
-     return TRUE;