Increase JS heap

[seanf]

JIRA issue URL: paste URL here

Apparently the default for Node is 1.76GB on 64 bit machines: https://stackoverflow.com/questions/47381275/why-does-node-js-have-an-1-76-gb-memory-limit?rq=1

This change increases it to 4GB when built via Jenkins.

Checklist

• JIRA link
• Check target branch
• Make sure all commit statuses are green or otherwise documented reasons to ignore
• QA needs to evaluate against the JIRA ticket
• Changed files and commits make sense for this PR

See Zanata Development Guidelines more for information.

---

This template can be updated in .github/PULL_REQUEST_TEMPLATE.md

[zubot]

This change is 

[djansen-redhat]

Reviewed 1 of 1 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[djansen-redhat]

@seanf NO_QA, rebuild maybe 3-5 times and go?

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@69ebf6b). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1032   +/-   ##
=========================================
  Coverage          ?   36.99%           
  Complexity        ?     6153           
=========================================
  Files             ?     1647           
  Lines             ?    65376           
  Branches          ?     7615           
=========================================
  Hits              ?    24184           
  Misses            ?    39094           
  Partials          ?     2098

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 69ebf6b...13c2524. Read the comment docs.

[alex-sl-eng]

Reviewed 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved

[alex-sl-eng]

Reviewable status: complete! all files reviewed, all discussions resolved

[seanf]

@djansen-redhat That's five builds in a row where the frontend module has finished without "JavaScript heap out of memory".