Fix typo (Geo.title --> Guide.title)

[arvindh-manian]

Fixes #1341

Contributor checklist:

• I've built the docs and confirmed these changes don't cause new errors

Proposed changes

• Change Geo.title to Guide.title

[codecov-io]

Codecov Report

Merging #1380 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1380   +/-   ##
=======================================
  Coverage   90.57%   90.57%           
=======================================
  Files          39       39           
  Lines        3988     3988           
=======================================
  Hits         3612     3612           
  Misses        376      376

Impacted Files	Coverage Δ
src/guide.jl	90.9% <ø> (ø)	⬆️

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[bjarthur]

thanks! let us know if you find anything else.