Remove "rclrs" duplicate dependency (backport #1197)

[mergify]

Description

There is already rclrs dependency defined in Cargo.toml.em template file. Currently when trying to build package user gets duplication error:

error: duplicate key
  --> Cargo.toml:18:1
   |
18 | rclrs = "*"
   | ^^^^^

Is this user-facing behavior change?

Correct Cargo.toml file.

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Additional Information

---

This is an automatic backport of pull request #1197 done by [Mergify](https://mergify.com).

[ahcorde]

Pulls: #1198
Gist: https://gist.githubusercontent.com/ahcorde/179bfe499f307ac7c86f7333c7c98a4c/raw/52c32c1d902a9b41791ebed71d660b002f7578d0/ros2.repos
BUILD args: --packages-above-and-dependencies ros2pkg
TEST args: --packages-above ros2pkg
ROS Distro: kilted
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18326

• Linux
• Linux-aarch64
• Linux-rhel
• Windows