Only remove excessive line breaks in assignments

[lorenzwalthert]

Closes #808.

[MichaelChirico]

Glad it was an easy fix! LGTM

[codecov-commenter]

Codecov Report

Merging #809 (4a74bfe) into master (9d376c4) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #809   +/-   ##
=======================================
  Coverage   90.46%   90.46%           
=======================================
  Files          47       47           
  Lines        2433     2433           
=======================================
  Hits         2201     2201           
  Misses        232      232           

Impacted Files	Coverage Δ
R/rules-line-breaks.R	100.00% <100.00%> (ø)

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[github-actions]

This is how benchmark results would change (along with a 95% confience interval in relative change) if e408eef is merged into master:

• cache_applying: 0.06s -> 0.06s [-3.34%, +2.94%]
• cache_recording: 1.48s -> 1.47s [-1.7%, +0.83%]
• without_cache: 3.89s -> 3.87s [-1.76%, +0.45%]

Further explanation regarding interpretation and methodology can be found in the documentation.