Removes cd to /src from instructions in README.

We normally call (and probably want to call) colcon from the root of the workspace
and not ./src (and definitely not /src).

Author: James Pace

README.md

@@ -54,7 +54,6 @@ mkdir src
 git clone https://github.com/ros2-rust/ros2_rust.git src/ros2_rust
 vcs import src < src/ros2_rust/ros2_rust_foxy.repos
 . /opt/ros/foxy/setup.sh
-cd /src
 colcon build --packages-up-to rclrs_examples
 ```