chore: rm two more unused vars

[maelle]

No description provided.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 0d54042 is merged into main:

• ✔️as_adjacency_matrix: 771ms -> 772ms [-1.14%, +1.27%]
• ✔️as_biadjacency_matrix: 745ms -> 747ms [-0.53%, +0.8%]
• ✔️as_data_frame_both: 1.49ms -> 1.48ms [-2.33%, +1.28%]
• ✔️as_long_data_frame: 3.92ms -> 3.91ms [-1.66%, +0.93%]
• ✔️es_attr_filter: 2.69ms -> 2.71ms [-1.61%, +2.77%]
• ✔️graph_from_adjacency_matrix: 121ms -> 121ms [-1.66%, +1.68%]
• ✔️graph_from_data_frame: 3.46ms -> 3.5ms [-2.02%, +4.33%]
• ✔️vs_attr_filter: 1.54ms -> 1.54ms [-2.65%, +1.85%]
• ✔️vs_by_name: 974µs -> 980µs [-1.88%, +3.04%]
  Further explanation regarding interpretation and methodology can be found in the documentation.