Remove shuheiktgw from maintainers (#3573)

Signed-off-by: shuheiktgw <s-kitagawa@mercari.com>

.github/PAUL.yaml

@@ -5,7 +5,6 @@ maintainers:
 - sebagomez
 - rodrmartinez
 - IdanAdar
-- shuheiktgw
 - skarlso
 - rogertuma
 # Emeritus Approvers