autoexport: Rename IsNone to IsNoneSpanExporter

[pellared]

Fixes #4133

[codecov]

Codecov Report

Merging #4134 (b9e1f71) into main (40b91b8) will decrease coverage by 0.1%.
Report is 1 commits behind head on main.
The diff coverage is 100.0%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4134     +/-   ##
=======================================
- Coverage   79.3%   79.3%   -0.1%     
=======================================
  Files        166     166             
  Lines      10330   10330             
=======================================
- Hits        8200    8197      -3     
- Misses      1996    1998      +2     
- Partials     134     135      +1     

Files Changed	Coverage Δ
exporters/autoexport/exporter.go	85.0% <ø> (ø)
exporters/autoexport/noop.go	42.8% <100.0%> (ø)

... and 1 file with indirect coverage changes