Remove spaces before square braces

[lorenzwalthert]

Closes #712. Just two minor cases.

[codecov-io]

Codecov Report

Merging #713 (d92448a) into master (f840c15) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #713      +/-   ##
==========================================
+ Coverage   90.46%   90.48%   +0.02%     
==========================================
  Files          47       47              
  Lines        2254     2259       +5     
==========================================
+ Hits         2039     2044       +5     
  Misses        215      215              

Impacted Files	Coverage Δ
R/rules-line-breaks.R	100.00% <100.00%> (ø)
R/rules-spaces.R	98.36% <100.00%> (ø)
R/style-guides.R	100.00% <100.00%> (ø)

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