updated deps & datastore needs Sync

[jrapoport]

updated deps.

Datastore interface no requires Sync method. returning nil as a no-op is fine and what MapDatastore does:
https://github.com/ipfs/go-datastore/blob/123d227a8d53b7e5d5c59c86b64efdeccb9dcc2f/basic_ds.go#L33

func (d *Datastore) Sync(_ datastore.Key) error {
	return nil // no-op
}

[codecov]

Codecov Report

Merging #14 (a08e252) into master (a2ca263) will decrease coverage by 2.90%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #14      +/-   ##
==========================================
- Coverage   84.38%   81.49%   -2.89%     
==========================================
  Files           1        1              
  Lines          64       54      -10     
==========================================
- Hits           54       44      -10     
  Misses          7        7              
  Partials        3        3              

Impacted Files	Coverage Δ
datastore.go	81.49% <0.00%> (-2.89%)	⬇️

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