chore(velocity_smoother): add maintainer (autowarefoundation#8121)

add maintainer

Signed-off-by: Go Sakayori <go.sakayori@tier4.jp>

Author: go-sakayori

planning/autoware_velocity_smoother/package.xml

@@ -9,6 +9,7 @@
   <maintainer email="takamasa.horibe@tier4.jp">Takamasa Horibe</maintainer>
   <maintainer email="makoto.kurihara@tier4.jp">Makoto Kurihara</maintainer>
   <maintainer email="satoshi.ota@tier4.jp">Satoshi Ota</maintainer>
+  <maintainer email="go.sakayori@tier4.jp">Go Sakayori</maintainer>
   <license>Apache License 2.0</license>
 
   <author email="takamasa.horibe@tier4.jp">Takamasa Horibe</author>