Set OPEN_TIMEOUT_IN_SECONDS

`dependabot-core` relies upon this value to give customers that need
more time in establishing connections. This value will be absorbed by
`dependabot-updater` and passed along.

Defaulting to a value of 10 as that's what we used in our connectivity
check. That value was sufficient for users which such concerns in the
past.

src/updater-builder.ts

@@ -50,7 +50,8 @@ export class UpdaterBuilder {
         `HTTP_PROXY=${this.proxy.url}`,
         `https_proxy=${this.proxy.url}`,
         `HTTPS_PROXY=${this.proxy.url}`,
-        `ENABLE_CONNECTIVITY_CHECK=1`
+        `ENABLE_CONNECTIVITY_CHECK=1`,
+        `OPEN_TIMEOUT_IN_SECONDS=10`
       ],
       Cmd: ['sh', '-c', cmd],
       HostConfig: {