base64 Dependency duplication

[pinkforest]

This can be resolved at upstream did-key to bump libsecp256k1 to ^0.7.1 which has bumped base64 to ^0.13

Current did-key at ^0.2.0 this only bumps libsecp256k1 to ^0.5.0 which is the problem meanwhile it itself uses base64 at ^0.13

warning[B004]: found 2 duplicate entries for crate 'base64'
   ┌─ /home/foobar/pp/fission-cli/Cargo.lock:9:1
   │  
 9 │ ╭ base64 0.12.3 registry+https://github.com/rust-lang/crates.io-index
10 │ │ base64 0.13.0 registry+https://github.com/rust-lang/crates.io-index
   │ ╰───────────────────────────────────────────────────────────────────^ lock entries
   │  
   = base64 v0.12.3
     └── libsecp256k1 v0.5.0
         └── did-key v0.1.1
             └── fission v0.1.0
   = base64 v0.13.0
     ├── did-key v0.1.1
     │   └── fission v0.1.0
     └── fission v0.1.0 (*)

[pinkforest]

I raised with upstream at: decentralized-identity/did-key.rs#36

Also PR for upstream to merge: decentralized-identity/did-key.rs#37

[pinkforest]

Upstream has merged bump, waiting for a release.