Rename validity variable

[what-the-diff[bot]]

PR Summary

• Update of Variable Names in WebRTCToken.php This update involved changing some variable names to ensure code readability and consistency. $maxValidityDurationSeconds was renamed to $maxlifeTimeSec and $validity was changed to $lifeTimeSec.

• Modification of method validFor() and expire() The method validFor() and expire() were redefined to incorporate the new variable names.

• Amendment in WebRTCTokenTest.php The tests in this file were updated to align with the changes made in WebRTCToken.php. The validity check has been altered to verify the new variable lifeTimeSec.

• Update of expire() method assertion Post the changes in 'WebRTCToken.php', the expire() method assertion was also updated to use the new variable name.

[codecov[bot]]

Codecov Report

Merging #75 (c3d758f) into main (c2534a3) will not change coverage. The diff coverage is 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #75 +/- ## ========================================= Coverage 88.28% 88.28% Complexity 428 428 ========================================= Files 78 78 Lines 1562 1562 ========================================= Hits 1379 1379 Misses 183 183 ```