elixir span docs: fix reference to attributes type

[tsloughter]

No description provided.

[codecov]

Codecov Report

Merging #336 (53545f4) into main (0df19fd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #336   +/-   ##
=======================================
  Coverage   39.75%   39.75%           
=======================================
  Files          54       54           
  Lines        3655     3655           
=======================================
  Hits         1453     1453           
  Misses       2202     2202           

Flag	Coverage Δ
api	67.28% <ø> (ø)
elixir	16.44% <ø> (ø)
erlang	39.79% <ø> (ø)
exporter	19.98% <ø> (ø)
sdk	77.44% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
apps/opentelemetry_api/lib/open_telemetry.ex	21.42% <ø> (ø)
apps/opentelemetry_api/lib/open_telemetry/span.ex	26.31% <ø> (ø)
...pps/opentelemetry_api/lib/open_telemetry/tracer.ex	37.50% <ø> (ø)

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[tsloughter]

Added on a commit to fix some of the example code in the api.