nit: remove fallbackDeclaration.js

In the previous commit, I failed to remove this file.
This is a cleanup.

Test plan: `yarn test`

src/analysis/fallbackDeclaration.js

@@ -1,23 +0,0 @@
-// @flow
-
-import {NodeAddress, EdgeAddress} from "../core/graph";
-
-import type {EdgeType, NodeType} from "./types";
-
-export const fallbackNodeType: NodeType = Object.freeze({
-  name: "node",
-  pluralName: "nodes",
-  prefix: NodeAddress.empty,
-  defaultWeight: 1,
-  description:
-    "The fallback NodeType for nodes which don't have any other type",
-});
-
-export const fallbackEdgeType: EdgeType = Object.freeze({
-  forwardName: "points to",
-  backwardName: "is pointed to by",
-  defaultWeight: {forwards: 1, backwards: 1},
-  prefix: EdgeAddress.empty,
-  description:
-    "The fallback EdgeType for edges which don't have any other type",
-});