chore(rtc_interface): add maintainer (#6235)

Signed-off-by: Fumiya Watanabe <rej55.g@gmail.com>

Author: rej55

planning/rtc_interface/package.xml

@@ -7,6 +7,7 @@
   <maintainer email="fumiya.watanabe@tier4.jp">Fumiya Watanabe</maintainer>
   <maintainer email="taiki.tanaka@tier4.jp">Taiki Tanaka</maintainer>
   <maintainer email="kyoichi.sugahara@tier4.jp">Kyoichi Sugahara</maintainer>
+  <maintainer email="satoshi.ota@tier4.jp">Satoshi Ota</maintainer>
 
   <license>Apache License 2.0</license>