message: [now-cli] Remove hard-refresh to rebuild for `now dev`
  This behavior is legacy from the very early days of `now dev`
  (before the `files` array was returned from Runtimes) and adds
  complexity. We can remove it at this point to simplify dev server.
diff: @@ -877,13 +877,6 @@ export default class DevServer {
  }
  }
  - shouldRebuild(req: http.IncomingMessage): boolean {
  - return (
  - req.headers.pragma === 'no-cache' ||
  - req.headers['cache-control'] === 'no-cache'
  - );
  - }
  -
  async send404(
  req: http.IncomingMessage,
  res: http.ServerResponse,
  @@ -1045,8 +1038,8 @@ export default class DevServer {
  filesChanged?: string[],
  filesRemoved?: string[]
  ) {
  - // If the requested asset wasn't found in the match's outputs, or
  - // a hard-refresh was detected, then trigger a build
  + // If the requested asset wasn't found in the match's
  + // outputs then trigger a build
  const buildKey =
  requestPath === null ? match.src : `${match.src}-${requestPath}`;
  let buildPromise = this.inProgressBuilds.get(buildKey);
  @@ -1056,14 +1049,6 @@ export default class DevServer {
  let msg = `De-duping build "${buildKey}"`;
  if (req) msg += ` for "${req.method} ${req.url}"`;
  this.output.debug(msg);
  - } else if (Date.now() - match.buildTimestamp < ms('2s')) {
  - // If the built asset was created less than 2s ago, then don't trigger
  - // a rebuild. The purpose of this threshold is because once an HTML page
  - // is rebuilt, then the CSS/JS/etc. assets on the page are also refreshed
  - // with a `no-cache` header, so this avoids *two* rebuilds for that case.
  - let msg = `Skipping build for "${buildKey}" (not older than 2s)`;
  - if (req) msg += ` for "${req.method} ${req.url}"`;
  - this.output.debug(msg);
  } else {
  const nowConfig = await this.getNowConfig();
  if (previousBuildResult) {
  @@ -1266,10 +1251,10 @@ export default class DevServer {
  }
  let foundAsset = findAsset(match, requestPath, nowConfig);
  - if ((!foundAsset || this.shouldRebuild(req)) && callLevel === 0) {
  + if (!foundAsset && callLevel === 0) {
  await this.triggerBuild(match, buildRequestPath, req);
  - // Since the `asset` was re-built, resolve it again to get the new asset
  + // Since the `asset` was just built, resolve again to get the new asset
  foundAsset = findAsset(match, requestPath, nowConfig);
  }
  