Cleanup warnings and bump minor versions

[david-driscoll]

Updated to latest minor versions of system.reactive, collections.immutable and nerdbank.streams

[codecov]

Codecov Report

Merging #760 (7c1311d) into master (aacb0ba) will decrease coverage by 0.86%.
The diff coverage is 65.38%.

@@            Coverage Diff             @@
##           master     #760      +/-   ##
==========================================
- Coverage   73.21%   72.34%   -0.87%     
==========================================
  Files         254      254              
  Lines       12554    12820     +266     
  Branches      807      805       -2     
==========================================
+ Hits         9191     9275      +84     
- Misses       3363     3545     +182     

Impacted Files	Coverage Δ
src/Dap.Client/DebugAdapterClientOptions.cs	6.25% <0.00%> (-10.42%)	⬇️
...erators/AssemblyCapabilityKeyAttributeGenerator.cs	1.31% <0.00%> (-0.25%)	⬇️
...ators/AssemblyJsonRpcHandlersAttributeGenerator.cs	2.77% <0.00%> (-0.21%)	⬇️
src/JsonRpc/DefaultJsonRpcServerFacade.cs	0.00% <0.00%> (ø)
src/JsonRpc/NoopResponseRouter.cs	0.00% <0.00%> (ø)
src/Protocol.Proposals/ProposedExtensions.cs	100.00% <ø> (ø)
...l.Proposals/Serialization/ProposedLspSerializer.cs	93.33% <ø> (ø)
...rc/Server/Pipelines/SemanticTokensDeltaPipeline.cs	100.00% <ø> (ø)
...nRpc/Serialization/Converters/RpcErrorConverter.cs	78.12% <16.66%> (-14.98%)	⬇️
src/JsonRpc/IActivityTracingStrategy.cs	8.33% <21.15%> (+0.20%)	⬆️
... and 29 more

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