internal/gophers: add mpratt's GitHub user for gomote

Change-Id: I9c801003479af62ee2c31d445f9eff6c9421c226
Reviewed-on: https://go-review.googlesource.com/c/build/+/234218
Run-TryBot: Alexander Rakoczy <alex@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/internal/gophers/gophers.go b/internal/gophers/gophers.go
index fe1316d..8a18e96 100644
--- a/internal/gophers/gophers.go
+++ b/internal/gophers/gophers.go
@@ -3207,6 +3207,8 @@
 		return "randall77"
 	case "lazard":
 		return "davidlazar"
+	case "mpratt":
+		return "prattmic"
 	case "pjw":
 		return "pjweinbgo"
 	case "r":