Update documentation of prvGetExpectedIdleTime (#1061)

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>

tasks.c

diff --git a/tasks.c b/tasks.c
index 3423bec..db158f6 100644
--- a/tasks.c
+++ b/tasks.c
@@ -662,7 +662,8 @@
 
 /*
  * Return the amount of time, in ticks, that will pass before the kernel will
- * next move a task from the Blocked state to the Running state.
+ * next move a task from the Blocked state to the Running state or before the
+ * tick count overflows (whichever is earlier).
  *
  * This conditional compilation should use inequality to 0, not equality to 1.
  * This is to ensure portSUPPRESS_TICKS_AND_SLEEP() can be called when user