📝 Fix RHEL install instructions to work. (#5498)

* 📝 Fix RHEL install instructions to work.

`sudo ... > ...` doesn't work, use the same `tee` trick as the deb instructions.

* 📝 Echo doesn't process \n by default.

docs/sources/flow/setup/install/linux.md

@@ -31,8 +31,8 @@ To install Grafana Agent in flow mode on Linux, run the following commands in a
    ```rhel-fedora
    wget -q -O gpg.key https://rpm.grafana.com/gpg.key
    sudo rpm --import gpg.key
-   sudo echo '[grafana]\nname=grafana\nbaseurl=https://rpm.grafana.com\nrepo_gpgcheck=1\nenabled=1\ngpgcheck=1\ngpgkey=https://rpm.grafana.com/gpg.key\nsslverify=1
-sslcacert=/etc/pki/tls/certs/ca-bundle.crt' > /etc/yum.repos.d/grafana.repo
+   echo -e '[grafana]\nname=grafana\nbaseurl=https://rpm.grafana.com\nrepo_gpgcheck=1\nenabled=1\ngpgcheck=1\ngpgkey=https://rpm.grafana.com/gpg.key\nsslverify=1
+sslcacert=/etc/pki/tls/certs/ca-bundle.crt' | sudo tee /etc/yum.repos.d/grafana.repo
    ```
 
    ```suse-opensuse