change -2 to -3 to align with the following graph and text AND remove duplicate word determine

[ascendho]

Fix issue I opened earlier：

The issue reports a discrepancy in the “Sequence Containers/Behind the Scenes” section of the CS106L textbook: the code snippet shows pushing -2 to the front of deque d, but the accompanying graph and explanatory text refer to pushing -3. The value used in the code does not match the value shown in the graph and text, and they should be made consistent.

Summary generated by Copilot:

This pull request makes a minor change to the sequence of values being pushed to the front of a container in the src/05-containers/01-sequence-containers.md file. The value -2 is replaced with -3 in the example.

[ascendho]

Fix issue I opened earlier：

The issue reports a discrepancy in the “Sequence Containers/Behind the Scenes” section of the CS106L textbook: the code snippet shows pushing -2 to the front of deque d, but the accompanying graph and explanatory text refer to pushing -3. The value used in the code does not match the value shown in the graph and text, and they should be made consistent.

Summary generated by Copilot:

This pull request makes a minor change to the sequence of values being pushed to the front of a container in the src/05-containers/01-sequence-containers.md file. The value -2 is replaced with -3 in the example.

Another issue I submitted.