Update the clone command

Users will get the following error, because they are not authorized to use the `git@github...` clone:

```bash
[email protected]: Permission denied (publickey).
fatal: Could not read from remote repository.
```

Users who want to try this out can use the following command instead:

```bash
$ $ git clone https://github.com/NVIDIA/Cosmos.git
Cloning into 'Cosmos'...
remote: Enumerating objects: 213, done.
remote: Counting objects: 100% (25/25), done.
remote: Compressing objects: 100% (22/22), done.
remote: Total 213 (delta 10), reused 11 (delta 2), pack-reused 188 (from 1)
Receiving objects: 100% (213/213), 8.02 MiB | 5.12 MiB/s, done.
Resolving deltas: 100% (29/29), done.

```

INSTALL.md

@@ -7,7 +7,7 @@ We have only tested the installation with Ubuntu 24.04, 22.04, and 20.04.
 2. Clone the repository.
 
 ```bash
-git clone git@github.com:NVIDIA/Cosmos.git
+git clone https://github.com/NVIDIA/Cosmos.git
 cd Cosmos
 ```