Remove hardcoded value (SlowMist N9)

[clostao]

Description

Slowmist problem description:

In the provided code, hardcoding an Ethereum address (an H160 value) directly within the default method is not
considered a good practice. This approach lack of flexibility and reduced maintainability.

fn default() -> Self {

    Self {
       initial_default_conversion_rate_controller: <H160 as
       core::str::FromStr>::from_str(
         "0x444212d6E4827893A70d19921E383130281Cda4a",
      )
      .expect("invalid address"),
     }
}

Our response:

Suggested changes were applied

Types of changes

What types of changes does your code introduce?

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)