Remove unnecessary build restrictions for go1.18

[bogdandrutu]

Signed-off-by: Bogdan Drutu bogdandrutu@gmail.com

[codecov]

Codecov Report

Merging #3197 (a1b4585) into main (038248b) will decrease coverage by 0.0%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3197     +/-   ##
=======================================
- Coverage   77.3%   77.2%   -0.1%     
=======================================
  Files        159     159             
  Lines      11101   11101             
=======================================
- Hits        8583    8579      -4     
- Misses      2323    2327      +4     
  Partials     195     195             

Impacted Files	Coverage Δ
bridge/opencensus/internal/ocmetric/metric.go	93.8% <ø> (ø)
exporters/otlp/otlpmetric/exporter.go	85.0% <ø> (ø)
exporters/otlp/otlpmetric/internal/otest/client.go	95.2% <ø> (ø)
...orters/otlp/otlpmetric/internal/otest/collector.go	7.2% <ø> (ø)
...rs/otlp/otlpmetric/internal/transform/attribute.go	100.0% <ø> (ø)
...orters/otlp/otlpmetric/internal/transform/error.go	100.0% <ø> (ø)
...s/otlp/otlpmetric/internal/transform/metricdata.go	100.0% <ø> (ø)
exporters/otlp/otlpmetric/otlpmetricgrpc/client.go	87.8% <ø> (ø)
exporters/otlp/otlpmetric/otlpmetricgrpc/config.go	35.2% <ø> (ø)
exporters/otlp/otlpmetric/otlpmetrichttp/client.go	78.8% <ø> (ø)
... and 24 more