docs(options): correct dimensions default

[TheSharpieOne]

Summary

The docs currently indicate that the default value for dimensions is false, but it appears to be true: https://github.com/smooth-code/svgr/blob/d112dd287fb1c369bc6caf97807369d827de5528/packages/core/src/config.js#L5
This caused some confusion.

Test plan

N/A

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[codecov]

Codecov Report

Merging #258 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #258   +/-   ##
=======================================
  Coverage   85.26%   85.26%           
=======================================
  Files          30       30           
  Lines         448      448           
  Branches      125      125           
=======================================
  Hits          382      382           
  Misses         55       55           
  Partials       11       11

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[codecov]

Codecov Report

Merging #258 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #258   +/-   ##
=======================================
  Coverage   85.26%   85.26%           
=======================================
  Files          30       30           
  Lines         448      448           
  Branches      125      125           
=======================================
  Hits          382      382           
  Misses         55       55           
  Partials       11       11

---

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 d112dd2...8e965b6. Read the comment docs.

[gregberge]

You are right! Nice catch!