Broken links in SDK client code

While making #1413 I noticed the following broken links. They point to old Nodejs docs which are now 404:

[packages/sdk-client/src/sdk-client/client.ts](https://github.com/commercetools/commercetools-sdk-typescript/blob/master/packages/sdk-client/src/sdk-client/client.ts)
- links to https://commercetools.github.io/nodejs/sdk/api/sdkClient.html#processrequest-processfn-options

[packages/sdk-client/src/sdk-client/validate.ts](https://github.com/commercetools/commercetools-sdk-typescript/blob/master/packages/sdk-client/src/sdk-client/validate.ts)
- links to https://commercetools.github.io/nodejs/sdk/Glossary.html#clientrequest - which I assume should now be https://commercetools.github.io/nodejs/sdk/Glossary/#clientrequest

[packages/sdk-client-v3/src/client/client.ts](https://github.com/commercetools/commercetools-sdk-typescript/blob/master/packages/sdk-client-v3/src/client/client.ts)
- links to https://commercetools.github.io/nodejs/sdk/api/sdkClient.html#processrequest-processfn-options

[packages/sdk-client-v3/src/utils/validate.ts](https://github.com/commercetools/commercetools-sdk-typescript/blob/master/packages/sdk-client-v3/src/utils/validate.ts)
- links to https://commercetools.github.io/nodejs/sdk/Glossary.html#clientrequest - which I assume should now be https://commercetools.github.io/nodejs/sdk/Glossary/#clientrequest

Start by inspecting the four named files: packages/sdk-client/src/sdk-client/client.ts, packages/sdk-client/src/sdk-client/validate.ts, packages/sdk-client-v3/src/client/client.ts, and packages/sdk-client-v3/src/utils/validate.ts. Search for the obsolete Node.js documentation URLs, update them to valid destinations, and verify that all referenced links resolve successfully.

Written by the indexing model from the issue text.