Consolidate the three Dijkstra implementations and remove the misplaced copy in `others/`

[DenizAltunkapan]

Description

Dijkstra's shortest-path algorithm is currently implemented three times:

• others/Dijkstra.java
• datastructures/graphs/DijkstraAlgorithm.java
• datastructures/graphs/DijkstraOptimizedAlgorithm.java

The copy in others/ is also misplaced — graph algorithms belong under datastructures/graphs/.

Proposed change

• Remove the duplicate in others/ (keeping its tests/edge cases if they add coverage).
• Keep a single canonical Dijkstra under datastructures/graphs/.

Note: the choice between the "Algorithm" and "Optimized" variants is tracked separately in a companion issue about unifying on the efficient priority-queue implementation.