Delete unused code

[khotyn]

Some code in TraceIdGenerator is not unused, so delete those code.

Motivation:

Explain the context, and why you're making that change.
To make others understand what is the problem you're trying to solve.

Modification:

Describe the idea and modifications you've done.

Result:

Fixes #.

If there is no issue then describe the changes introduced by this PR.

[coveralls]

Pull Request Test Coverage Report for Build 47

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+1.5%) to 48.397%

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Files with Coverage Reduction	New Missed Lines	%
tracer-core/src/main/java/com/alipay/common/tracer/core/generator/TraceIdGenerator.java	2	88.46%

Totals
Change from base Build 45:	1.5%
Covered Lines:	1555
Relevant Lines:	3213

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💛 - Coveralls