chore: update code for get pending txn

[renlulu]

Description

Update error map for GetPendingTxn according to https://dev.zilliqa.com/docs/apis/api-transaction-get-transaction-status/

Review Suggestion

Status

Implementation

• ready for review

[codecov-commenter]

Codecov Report

Merging #292 (feabeea) into dev (b0d6ece) will not change coverage.
The diff coverage is n/a.

❗ Current head feabeea differs from pull request most recent head aff20df. Consider uploading reports for the commit aff20df to get more accurate results

@@           Coverage Diff           @@
##              dev     #292   +/-   ##
=======================================
  Coverage   78.06%   78.06%           
=======================================
  Files          45       45           
  Lines        1682     1682           
  Branches      272      272           
=======================================
  Hits         1313     1313           
  Misses        365      365           
  Partials        4        4           

Impacted Files	Coverage Δ
packages/zilliqa-js-blockchain/src/chain.ts	55.55% <ø> (ø)

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[bb111189]

We will need to remove getpendingtxn and retain getpendingtxns

[bb111189]

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