Replace git clone SSH URI with HTTPS URL

Running `git clone --recurse-submodules git@github.com:nomic-ai/gpt4all.git`
returns `Permission denied (publickey)` as shown below:
```
git clone --recurse-submodules git@github.com:nomic-ai/gpt4all.git
Cloning into gpt4all...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.
```

This change replaces `git@github.com:nomic-ai/gpt4all.git` with
`https://github.com/nomic-ai/gpt4all.git` which runs without permission issues.

resolves nomic-ai/gpt4all#8, resolves nomic-ai/gpt4all#49

gpt4all-bindings/python/README.md

@@ -20,7 +20,7 @@ pip install gpt4all
 1. Setup `llmodel`
 
 ```
-git clone --recurse-submodules git@github.com:nomic-ai/gpt4all.git
+git clone --recurse-submodules https://github.com/nomic-ai/gpt4all.git
 cd gpt4all/gpt4all-backend/
 mkdir build
 cd build