fix(contented-processor): fix getPipelineUniqueKey

[fuxingloh]

What this PR does / why we need it:

As per title.

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[codecov]

Codecov Report

Merging #552 (584acbe) into main (189d065) will decrease coverage by 1.65%.
Report is 13 commits behind head on main.
The diff coverage is 74.57%.

@@            Coverage Diff             @@
##             main     #552      +/-   ##
==========================================
- Coverage   86.64%   85.00%   -1.65%     
==========================================
  Files          10       10              
  Lines         397      420      +23     
  Branches       65       73       +8     
==========================================
+ Hits          344      357      +13     
- Misses         53       63      +10     

Files Changed	Coverage Δ
...es/contented-pipeline-md/src/plugins/RemarkLink.ts	71.42% <45.45%> (-28.58%)	⬇️
packages/contented-pipeline/src/Pipeline.ts	85.33% <62.50%> (-3.24%)	⬇️
...ages/contented-processor/src/ContentedProcessor.ts	86.41% <66.66%> (+0.52%)	⬆️
...ages/contented-pipeline-md/src/MarkdownPipeline.ts	85.29% <82.35%> (-0.92%)	⬇️
...ented-pipeline-jest-md/src/JestMarkdownPipeline.ts	100.00% <100.00%> (ø)
...ckages/contented-processor/src/ContentedCodegen.ts	100.00% <100.00%> (ø)