Remove einsum in forward pass in AbstractAttention #1747

Job	Run time
Compatibility Checks (3.9)	9m 26s
Code Checks	6m 43s
Notebook Checks (ARENA_Content)	1m 26s
Compatibility Checks (3.10)	10m 26s
Notebook Checks (Colab_Compatibility)	1m 18s
Notebook Checks (BERT)	1m 7s
Notebook Checks (Exploratory_Analysis_Demo)	5m 16s
Notebook Checks (Interactive_Neuroscope)	1m 11s
Notebook Checks (Main_Demo)	1m 41s
Notebook Checks (Othello_GPT)	1m 7s
Notebook Checks (Patchscopes_Generation_Demo)	6m 45s
Build Docs	0s
Deploy Docs	0s
	46m 26s

Provide feedback