Update the readme for installation

[SyedMurtazaHassan46]

Update the readme with the new installation process that is more streamlined and remove any unnecessary step. The following things need to be changed:

• Remove the cloning step and add instruction on how to use helm to install XkOps
• Update instruction related to values.yaml file, including how to create it, what it should include and where to pass it in the helm command
• Remove Step 5 which is unnecessary
• Add instructions to update the secrets in AWS Secret Manager, including slack key and robusta key

[SyedMurtazaHassan46]

Here is a picture of what the installation guide will be updated to kindly review and notify if any changes are required.