Remove the YAML parameter `acceptance`

[wehs7661]

In the updated theory, there is only one way to calculate the acceptance ratio assuming symmetric proposal probabilities. Previously we removed the option metropolis_eq/metropolis-eq from the YAML parameter acceptance and we decided to remove the state-state swapping scheme, which leaves only one option (metropolis) for the parameter acceptance and makes the parameter acceptance not necessary anymore. Therefore, the YAML parameter acceptance should be removed and the documentation should be updated accordingly.

[wehs7661]

The commit a3f07fc has addressed the issue.