Remove github/loadGithubData (#1596)

The function is marked deprecated and has no usage in the codebase.

Test plan: `yarn test` passes.

src/plugins/github/loadGithubData.js

@@ -1,43 +0,0 @@
-// @flow
-
-import fs from "fs-extra";
-import path from "path";
-import pako from "pako";
-
-import fetchGithubRepo from "./fetchGithubRepo";
-import {RelationalView} from "./relationalView";
-import type {RepoId} from "./repoId";
-
-export type Options = {|
-  +token: string,
-  +repoIds: $ReadOnlyArray<RepoId>,
-  +outputDirectory: string,
-  +cacheDirectory: string,
-|};
-
-// This function is deprecated.
-export async function loadGithubData(options: Options): Promise<void> {
-  // We intentionally fetch repositories sequentially rather than in
-  // parallel, because GitHub asks that we not make concurrent
-  // requests. From <https://archive.is/LlkQp#88%>:
-  //
-  // > Make requests for a single user or client ID serially. Do not make
-  // > make requests for a single user or client ID concurrently.
-  const responses = [];
-  for (const repoId of options.repoIds) {
-    responses.push(
-      await fetchGithubRepo(repoId, {
-        token: options.token,
-        cacheDirectory: options.cacheDirectory,
-      })
-    );
-  }
-  const view = new RelationalView();
-  for (const response of responses) {
-    view.addRepository(response);
-  }
-  view.compressByRemovingBody();
-  const blob: Uint8Array = pako.gzip(JSON.stringify(view));
-  const outputFilename = path.join(options.outputDirectory, "view.json.gz");
-  return fs.writeFile(outputFilename, blob);
-}