fixed wrong link in examples notebooks

[Ezpeon]

The previous links did not navigate the folders correctly to access the example notebooks

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 68.96552% with 9 lines in your changes missing coverage. Please review.

Project coverage is 85.32%. Comparing base (7bd297e) to head (22373ba). Report is 12 commits behind head on master.

Files with missing lines	Patch %	Lines
...ngines/compilers/trajectory_constraints_remover.py	16.66%	5 Missing :warning:
...ning/engines/compilers/usertype_fluents_remover.py	33.33%	2 Missing :warning:
unified_planning/engines/compilers/utils.py	33.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #623 +/- ## ========================================== - Coverage 85.34% 85.32% -0.03% ========================================== Files 202 202 Lines 27272 27286 +14 ========================================== + Hits 23275 23281 +6 - Misses 3997 4005 +8 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.