Update my committer name and add my new mentor relationship

## Regarding the name change

A few years ago I changed my legal name to "Enji Cooper". When I rejoined the
project, I requested that accounts@ use my legal name instead of my [previous]
nickname. This change syncs up a reference to use the proper name for clarity.

## Regarding the new mentor relationship

@emaste and @jtl graciously accepted my request to mentor me this time around
with my src commits while I get up to speed.

I am leaving my previous mentorship details in committers-src.dot for historical
reasons, per @emaste's request.

-- Thank you very much @jmmv and @rpaulo for the help with my previous
   mentorship; I really appreciate it!

Approved by:	emaste (mentor)
Differential Revision:	https://reviews.freebsd.org/D18644

share/misc/committers-src.dot

@@ -266,7 +266,7 @@ mr [label="Michael Reifenberger\nmr@FreeBSD.org\n2001/09/30"]
 mw [label="Marcin Wojtas\nmw@FreeBSD.org\n2017/07/18"]
 neel [label="Neel Natu\nneel@FreeBSD.org\n2009/09/20"]
 netchild [label="Alexander Leidinger\nnetchild@FreeBSD.org\n2005/03/31"]
-ngie [label="Ngie Cooper\nngie@FreeBSD.org\n2014/07/27"]
+ngie [label="Enji Cooper\nngie@FreeBSD.org\n2014/07/27"]
 nork [label="Norikatsu Shigemura\nnork@FreeBSD.org\n2009/06/09"]
 np [label="Navdeep Parhar\nnp@FreeBSD.org\n2009/06/05"]
 nwhitehorn [label="Nathan Whitehorn\nnwhitehorn@FreeBSD.org\n2008/07/03"]
@@ -503,6 +503,7 @@ emaste -> dteske
 emaste -> kevans
 emaste -> lwhsu
 emaste -> markj
+emaste -> ngie
 emaste -> rstone
 
 emax -> markus
@@ -637,6 +638,7 @@ joerg -> le
 joerg -> netchild
 joerg -> schweikh
 
+jtl -> ngie
 jtl -> thj
 
 julian -> glebius