Delete vestigial chunk preloading code

[rtsao]

Newer fusion-cli versions don't need this custom code anymore. See fusionjs/fusion-cli#451 for more context.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@a6145ba). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #273   +/-   ##
=========================================
  Coverage          ?   92.25%           
=========================================
  Files             ?       18           
  Lines             ?      400           
  Branches          ?       76           
=========================================
  Hits              ?      369           
  Misses            ?       17           
  Partials          ?       14

Impacted Files	Coverage Δ
src/plugins/ssr.js	94.82% <100%> (ø)

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[KevinGrandon]

Whoa, it's so simple now 😍

[rtsao]

!merge