libsel4test: Remove seL4_timer_t from env

This struct member was not being used anywhere at all, so we remove it.

libsel4test/include/sel4test/test.h

diff --git a/libsel4test/include/sel4test/test.h b/libsel4test/include/sel4test/test.h
index 86adc3a..d4122d3 100644
--- a/libsel4test/include/sel4test/test.h
+++ b/libsel4test/include/sel4test/test.h
@@ -46,8 +46,6 @@
     vka_t vka;
     /* virtual memory management interface */
     vspace_t vspace;
-    /* initialised timer */
-    seL4_timer_t timer;
     /* abstract interface over application init */
     simple_t simple;
     /* notification for timer */