chore: bump typescript version to ^3.7.2

[dyladan]

Which problem is this PR solving?

• Fix build failures on latest typescript
• Bump to latest typescript

Short description of the changes

1. Update typescript version to ^3.7.2 in all package.json files
2. Remove unreachable code from dns plugin test
3. Remove always-true if-statement from grpc plugin

REVIEWERS PLEASE PAY PARTICULAR ATTENTION TO POINTS 2 AND 3

[codecov-io]

Codecov Report

Merging #497 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #497      +/-   ##
==========================================
- Coverage   94.98%   94.93%   -0.05%     
==========================================
  Files         136      136              
  Lines        6482     6381     -101     
  Branches      567      570       +3     
==========================================
- Hits         6157     6058      -99     
+ Misses        325      323       -2

Impacted Files	Coverage Δ
...in-dns/test/integrations/dnspromise-lookup.test.ts	91.58% <ø> (+1.68%)	⬆️
packages/opentelemetry-plugin-grpc/src/grpc.ts	96.23% <100%> (-0.05%)	⬇️
...ages/opentelemetry-plugin-http/test/utils/utils.ts	33.33% <0%> (-26.67%)	⬇️
...es/opentelemetry-node/src/instrumentation/utils.ts	90.47% <0%> (-9.53%)	⬇️
...ges/opentelemetry-tracing/src/NoopSpanProcessor.ts	66.66% <0%> (-8.34%)	⬇️
packages/opentelemetry-tracing/src/config.ts	100% <0%> (ø)	⬆️
packages/opentelemetry-tracing/src/utility.ts	100% <0%> (ø)	⬆️
...entelemetry-exporter-jaeger/test/transform.test.ts	100% <0%> (ø)	⬆️
packages/opentelemetry-tracing/test/Span.test.ts	100% <0%> (ø)	⬆️
packages/opentelemetry-metrics/src/Utils.ts	100% <0%> (ø)	⬆️
... and 12 more

[mayurkale22]

LGTM 💯