update README about BoundedMean function

[tak-ka3]

Description

What is written in README.md file is old. So I updated it.
First of all, the execution of BoundedMean(0.6, 1, 10) has an error, because the arguments of BoundedMean function are epsilon: float = 1.0, delta: float = 0, lower_bound: Union[int, float, None] = None, upper_bound: Union[int, float, None] = None, l0_sensitivity: int = 1, linf_sensitivity: int = 1, dtype: str = "int" in order. So the second argument of BoundedMean(0.6, 1, 10) is incompatible to delta, which should be float type not integer type.

Also the type of epsilon should be float not double, and modify some names of arguments like from lower to lower_bound.

Affected Dependencies

None.

[chinmayshah99]

good catch! thank you @tak-ka3 for the PR :)