[ci] fix cannot find Threads on Android

[wgtdkp]

pthread is already included in Android glibc implementation (bionic), so there is no necessary to find the thread libs separately.

Reference: https://stackoverflow.com/questions/5990661/cmake-find-packagethreads-for-android-cross-compilation

[codecov-commenter]

Codecov Report

Merging #233 (73bcc50) into main (6d142e8) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 73bcc50 differs from pull request most recent head 0ceef1c. Consider uploading reports for the commit 0ceef1c to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #233 +/- ## ======================================= Coverage 74.02% 74.02% ======================================= Files 76 76 Lines 7553 7553 ======================================= Hits 5591 5591 Misses 1962 1962 ```