v5.2.0-ago.7: edge-helm-charts: import isomorphic-git http via the public subpath

Commit 55659de8 pinned the import to `isomorphic-git/http/node/index.cjs`
to work around an ESM resolution failure after the dep was bumped in
861ed714. That workaround is no longer valid: current isomorphic-git
publishes a strict `exports` map that exposes only `./http/node`
(auto-resolves to index.js for ESM consumers, index.cjs for require),
not the deep `/index.cjs` path. The bumped image fails on import:

  Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath
  './http/node/index.cjs' is not defined by "exports" in
  /home/node/app/node_modules/isomorphic-git/package.json

Revert to the bare `./http/node` subpath the package actually exports.