chore: remove hardcoded testnet messages

[elsakarvouni]

Removed all hardcoded messages connecting to Hedera testnet.
Now the network is read from .env (NETWORK variable), so the message dynamically shows which network the user is connecting to.

[exploreriii]

Thank you so much, we require a changelog entry (see changelog.md) and all commits to be verified (see signing.md).
Thanks so much

[exploreriii]

Your latest commit is not verified
i'd recommend reverting and signing again

git reset --soft HEAD~4
git commit -S -s - m "....."

[exploreriii]

We do not recommend merges from main, please review README.md, CONTRIBUTING.md and workflow.md
you often lose sign status whne you do that

please note

I'm happy to discuss a solution, please read discord.md to learn about our discord

[exploreriii]

Hi @elsakarvouni an update working on examples was pushed, but you will need to rebase (see rebasing.md) and resolve some conflicts (see merge_conflicts.md).
It is a good opportunity to learn how to do that, but if it is difficult i'd recommend starting a fresh copy