Update Graph Search algorithm in AIMA4e

Currently, [GraphSearch.java](https://github.com/aimacode/aima-java/blob/AIMA4e/core/src/main/java/aima/core/search/basic/uninformed/GraphSearch.java) does not follow the [pseudo code](https://github.com/aimacode/aima-pseudocode/blob/master/md/Tree-Search-and-Graph-Search.md) of Graph Search algorithm of 4th edition.
@samagra14 I want to work on this issue. May I proceed?