docs: fix podman commands

Author: josecelano

README.md

@@ -45,7 +45,7 @@ docker run -it torrust/tracker:develop
 #### Podman:
 
 ```sh
-podman run -it torrust/tracker:develop
+podman run -it docker.io/torrust/tracker:develop
 ```
 > Please read our [container guide][containers.md] for more information.
 

docs/containers.md

@@ -14,7 +14,7 @@ docker run -it torrust/tracker:latest
 or with Podman:
 
 ```sh
-podman run -it torrust/tracker:latest
+podman run -it docker.io/torrust/tracker:latest
 ```
 
 
@@ -122,10 +122,10 @@ docker run -it torrust-tracker:debug
 
 ```sh
 # Release Mode
-podman run -it torrust-tracker:release
+podman run -it docker.io/torrust-tracker:release
 
 # Debug Mode
-podman run -it torrust-tracker:debug
+podman run -it docker.io/torrust-tracker:debug
 ```
 
 ### Arguments
@@ -226,7 +226,7 @@ podman run -it \
     --volume ./storage/tracker/lib:/var/lib/torrust/tracker:Z \
     --volume ./storage/tracker/log:/var/log/torrust/tracker:Z \
     --volume ./storage/tracker/etc:/etc/torrust/tracker:Z \
-    torrust-tracker:release
+    docker.io/torrust-tracker:release
 ```
 
 ## Docker Compose