remove sampler option to start_span and with_span

[tsloughter]

This was removed from the spec a loooooooooooooong time ago. Luckily we didn't add all those sampler options to libraries so hopefully this isn't an issue for many users? I have an OTEP almost ready for handling the use case of a specific sampler for a tracer.

[codecov]

Codecov Report

Merging #296 (0031138) into main (ead6ae1) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #296      +/-   ##
==========================================
- Coverage   37.35%   37.27%   -0.08%     
==========================================
  Files          46       46              
  Lines        3266     3262       -4     
==========================================
- Hits         1220     1216       -4     
  Misses       2046     2046              

Flag	Coverage Δ
api	65.14% <ø> (ø)
elixir	14.41% <ø> (ø)
erlang	37.27% <100.00%> (-0.08%)	⬇️
exporter	19.75% <ø> (ø)
sdk	76.58% <100.00%> (-0.17%)	⬇️

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Impacted Files	Coverage Δ
apps/opentelemetry/src/otel_span_utils.erl	88.00% <ø> (-0.47%)	⬇️
...pps/opentelemetry_api/lib/open_telemetry/tracer.ex	37.50% <ø> (ø)
apps/opentelemetry_api/src/otel_span.erl	66.66% <ø> (ø)
apps/opentelemetry/src/otel_span_ets.erl	64.86% <100.00%> (ø)
apps/opentelemetry/src/otel_tracer_default.erl	100.00% <100.00%> (ø)

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