starboard/types.h: Remove some unused types

[yell0wd0g]

As said, kSb(U)Int8(Min|Max) are not used anywhere [1]. This CL removes them. Verified bya local x64x11 build.

[1] https://source.corp.google.com/h/lbshell-internal/cobalt_src/+/COBALT:starboard/types.h?q=kSb.%3FInt(8)&ss=h%2Flbshell-internal%2Fcobalt_src%2F%2B%2Frefs%2Fheads%2FCOBALT

b/366064934

[yell0wd0g]

@y4vor PTAL - I thought this could be the smallest/trivial-est CL ever.

(For the other types, they can be replaced in this file with e.g.
std::numeric_limits<Bla>::min()/max() etc, or the substitutions
can be done at use/callsites. No need to decide here and now :)

[datadog-cobalt-youtube]

Datadog Report

Branch report: b_366064934__A__remove_unused_type_limits
Commit report: a824a7e
Test service: cobalt

✅ 0 Failed, 33731 Passed, 6 Skipped, 7m 23.81s Total Time

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 57.49%. Comparing base (0faa42d) to head (3a76d91).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4168      +/-   ##
==========================================
+ Coverage   57.48%   57.49%   +0.01%     
==========================================
  Files        1742     1742              
  Lines       86343    86330      -13     
==========================================
+ Hits        49632    49638       +6     
+ Misses      36711    36692      -19     

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