TBR: croupier: Remove .v23 from all .gitignore files.

MultiPart: 16/25

Change-Id: Ia594fc5116aac375ea02b313633c0804d2338ca1
diff --git a/.gitignore b/.gitignore
index 2872723..f6910de 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,4 @@
 /.jiri
-#TODO(nlacasse): Get rid of .v23 below once v23->jiri transition is complete.
-/.v23
 
 # Don't commit the bundled flutter app or snapshot.
 croupier.flx