TBR: mojo.discovery: Remove .v23 from all .gitignore files.

MultiPart: 11/25

Change-Id: Ifb2fc11c621e5c0dad6615c2c982cdf912e713ab
diff --git a/.gitignore b/.gitignore
index 3899f02..34b760f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,4 @@
 /.jiri
-#TODO(nlacasse): Get rid of .v23 below once v23->jiri transition is complete.
-/.v23
 /gen
 /lib/gen/dart-pkg
 /lib/gen/mojom