Shorten the XfaLayerBuilder.prototype.render method

[Snuffleupagus]

Given that the "print" intent is handled separately, there's currently a little bit of unnecessary code duplication in this method.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.40%. Comparing base (25c7d9e) to head (bd14524).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
web/xfa_layer_builder.js	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21317      +/-   ##
==========================================
+ Coverage   81.38%   81.40%   +0.02%     
==========================================
  Files         256      256              
  Lines       65328    65322       -6     
==========================================
+ Hits        53165    53177      +12     
+ Misses      12163    12145      -18     

Flag	Coverage Δ
integrationtest	66.98% <80.00%> (+0.02%)	⬆️
unittest	56.84% <0.00%> (-0.01%)	⬇️
unittestcli	56.05% <0.00%> (+<0.01%)	⬆️

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[timvandermeij]

Looks good; thank you!