Bump the date for when the commit bit expiration policy was last updated.

This bump is a followup of commit 89407529ff
Reported by:	lwhsu
Approved by:	core (implicit)

website/content/en/internal/expire-bits.adoc

@@ -7,7 +7,7 @@ sidenav: docs
 
 == Rationale
 
-Over time, FreeBSD committers may find other demands on their time, and decide that they wish to resign their commit bit. However, under some circumstances, a committer may become inactive over a long period of time without explicitly resigning their bit. Over the long term, these accounts can represent a security risk, as well as posing procedural questions regarding the degree to which contact information and access methods for the account are maintainable. For these reasons, the FreeBSD Core Team approved the following commit bit expiration policy, last updated on November 26, 2013.
+Over time, FreeBSD committers may find other demands on their time, and decide that they wish to resign their commit bit. However, under some circumstances, a committer may become inactive over a long period of time without explicitly resigning their bit. Over the long term, these accounts can represent a security risk, as well as posing procedural questions regarding the degree to which contact information and access methods for the account are maintainable. For these reasons, the FreeBSD Core Team approved the following commit bit expiration policy, last updated in November 2018.
 
 == Policy