Use true instead of One()

[mzgubic]

Going towards JuliaDiff/ChainRulesCore.jl#354

[codecov-commenter]

Codecov Report

Merging #416 (c23c6ad) into master (dffe76c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #416   +/-   ##
=======================================
  Coverage   98.49%   98.49%           
=======================================
  Files          23       23           
  Lines        1929     1929           
=======================================
  Hits         1900     1900           
  Misses         29       29           

Impacted Files	Coverage Δ
src/rulesets/Base/base.jl	100.00% <100.00%> (ø)
src/rulesets/Base/fastmath_able.jl	98.24% <100.00%> (ø)
src/rulesets/LinearAlgebra/symmetric.jl	99.61% <100.00%> (ø)

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[oxinabox]

Can a few of these be benchmarked to make sure it it doesn't introduce performance regressions?

Also it looks a bit funny to use true, should we add an explict note to @scalar_rule's docstring about this?

[mzgubic]

Can a few of these be benchmarked to make sure it it doesn't introduce performance regressions?

for reference JuliaDiff/ChainRulesCore.jl#357 (comment)