refactor: simplify track selection logic in AlignmentAlgorithm (#3934)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **Bug Fixes**
	- Improved logic for determining the number of tracks in the alignment process, enhancing clarity and efficiency.
- **Chores**
	- Maintained existing error handling for input collections, ensuring stability in case of empty collections.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Examples/Algorithms/Alignment/src/AlignmentAlgorithm.cpp

@@ -57,9 +57,9 @@ ActsExamples::ProcessCode ActsExamples::AlignmentAlgorithm::execute(
   }
 
   std::size_t numTracksUsed = protoTracks.size();
-  if (m_cfg.maxNumTracks > 0 &&
-      m_cfg.maxNumTracks < static_cast<int>(protoTracks.size())) {
-    numTracksUsed = m_cfg.maxNumTracks;
+  if (m_cfg.maxNumTracks > 0) {
+    numTracksUsed =
+        std::min(static_cast<std::size_t>(m_cfg.maxNumTracks), numTracksUsed);
   }
 
   // Prepare the input track collection