style(dpp): remove unused cbor import

[pshenmic]

Issue being fixed or feature implemented

CborCanonicalMap is not used anymore in the contract bounds, but still being imported in the file, making applications fail to build rs-dpp when used externally.

warning: `platform-serialization-derive` (lib) generated 2 warnings
   Compiling dpp v0.1.0 (/Users/pshenmic/WebstormProjects/platform/packages/rs-dpp)
error[E0432]: unresolved import `crate::util::cbor_value`
 --> /Users/pshenmic/WebstormProjects/platform/packages/rs-dpp/src/identity/identity_public_key/contract_bounds/mod.rs:5:18
  |
5 | use crate::util::cbor_value::{CborCanonicalMap, CborMapExtension};
  |                  ^^^^^^^^^^ could not find `cbor_value` in `util`

What was done?

Removed the crashing import line

How Has This Been Tested?

Removing this line makes rs-dpp to succesfully compile when used in external Rust project

Breaking Changes

No

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone