remove inline from ConnectionBaseNodelet::isSubscribed() #514

Job	Run time
ros-o (ubuntu:22.04, https://raw.githubusercontent.com/v4hn/ros-o-builder/jammy-one/repository)	7m 25s
ubuntu (ubuntu:22.04)	35m 57s
ros (indigo, jskrobotics/ros-ubuntu:14.04, -j8, sudo pip install virtualenv==15.1.0 setuptools==4...	17m 43s
ubuntu (ubuntu:24.04)	23m 4s
ros (kinetic, ubuntu:16.04, -j8)	17m 56s
ros (melodic, ubuntu:18.04, -j8)	20m 17s
ros (noetic, ubuntu:20.04, -j8)	26m 42s
ros (noetic, ubuntu:20.04, -j8, virtual_force_publisher, --cmake-args -DCMAKE_CXX_FLAGS=-std=c++1...	10m 57s
	2h 40m 1s

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