Revert "feat(db): add an index for SSHPubKeys.PubKey"

This reverts commit 1a7f6e1fa9.

This commit broke account creation in some way. We'd still like to
do this, but we need to ensure it does not intrude on other facets.

Extra: We should really work out how this even passed tests; it
should not have.

migrations/versions/dd70103d2e82_add_sshpubkeys_pubkey_index.py

@@ -1,28 +0,0 @@
-"""add SSHPubKeys.PubKey index
-
-Revision ID: dd70103d2e82
-Revises: d64e5571bc8d
-Create Date: 2022-08-12 21:30:26.155465
-
-"""
-import traceback
-
-from alembic import op
-
-# revision identifiers, used by Alembic.
-revision = 'dd70103d2e82'
-down_revision = 'd64e5571bc8d'
-branch_labels = None
-depends_on = None
-
-
-def upgrade():
-    try:
-        op.create_index("SSHPubKeysPubKey", "SSHPubKeys", ["PubKey"])
-    except Exception:
-        traceback.print_exc()
-        print("failing silently...")
-
-
-def downgrade():
-    op.drop_index("SSHPubKeysPubKey", "SSHPubKeys")