[Java 21] Fix testerina tests

[warunalakshitha]

Purpose

$Subject

Check List

• Read the Contributing Guide
• Updated Change Log
• Checked Tooling Support (#)
• Added necessary tests
  • Unit Tests
  • Spec Conformance Tests
  • Integration Tests
  • Ballerina By Example Tests
• Increased Test Coverage
• Added necessary documentation
  • API documentation
  • Module documentation in Module.md files
  • Ballerina By Examples

[codecov]

Codecov Report

Attention: Patch coverage is 71.11111% with 26 lines in your changes missing coverage. Please review.

Project coverage is 75.00%. Comparing base (8f6d65d) to head (fea2118).
Report is 119 commits behind head on java21.

Files with missing lines	Patch %	Lines
...llerina/runtime/internal/scheduling/Scheduler.java	76.47%	8 Missing ⚠️
.../ballerina/runtime/internal/scheduling/Strand.java	41.66%	6 Missing and 1 partial ⚠️
.../ballerina/runtime/internal/util/RuntimeUtils.java	44.44%	4 Missing and 1 partial ⚠️
.../ballerina/shell/invoker/ShellSnippetsInvoker.java	77.77%	2 Missing and 2 partials ⚠️
...java/io/ballerina/runtime/internal/BalRuntime.java	71.42%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             java21   #43406      +/-   ##
============================================
- Coverage     77.31%   75.00%   -2.31%     
+ Complexity    58532    56729    -1803     
============================================
  Files          3460     3447      -13     
  Lines        220050   218874    -1176     
  Branches      28902    28846      -56     
============================================
- Hits         170133   164177    -5956     
- Misses        40514    45743    +5229     
+ Partials       9403     8954     -449     

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