removing session tracking guard on hub and client

[marandaneto]

📢 Type of change

• Bugfix
• New feature
• Enhancement
• Refactoring

📜 Description

removing session tracking guard on hub and client.

💡 Motivation and Context

one would like to start and end sessions manually, but still having the automatic session tracking disabled.

💚 How did you test it?

📝 Checklist

• I reviewed submitted code
• [ ] I added tests to verify changes
• All tests passing

🔮 Next steps

[codecov-io]

Codecov Report

Merging #338 into master will decrease coverage by 0.13%.
The diff coverage is 94.73%.

@@             Coverage Diff              @@
##             master     #338      +/-   ##
============================================
- Coverage     59.07%   58.94%   -0.14%     
+ Complexity      766      762       -4     
============================================
  Files            87       87              
  Lines          3548     3539       -9     
  Branches        344      341       -3     
============================================
- Hits           2096     2086      -10     
- Misses         1300     1302       +2     
+ Partials        152      151       -1

Impacted Files	Coverage Δ	Complexity Δ
...re/src/main/java/io/sentry/core/SentryOptions.java	75.31% <ø> (-1.9%)	69 <0> (-2)
sentry-core/src/main/java/io/sentry/core/Hub.java	65.26% <ø> (-0.82%)	60 <0> (-2)
...ore/src/main/java/io/sentry/core/SentryClient.java	90.85% <94.73%> (+1.15%)	51 <8> (ø)	⬇️

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