Pin Nano to ~8.1.0 to prevent ts API breakage from 8.2.0

[ricellis]

Checklist

• [x] Tick to sign-off your agreement to the Developer Certificate of Origin (DCO) 1.1
• [x] Added tests for code changes or test/build only changes
• [x] Updated the change log file (CHANGES.md|CHANGELOG.md) or test/build only changes
• [x] Completed the PR template below:

Description

Nano 8.2 has some ts changes that break compatibility with nodejs-cloudant. It is currently an in-range update, but will break ts users, so we need to pin Nano to an older version.

1. Steps to reproduce and the simplest code sample possible to demonstrate the issue

Get latest dependencies and npm test

2. What you expected to happen

Checks to pass

3. What actually happened

types/index.d.ts:109:15 - error TS2430: Interface 'cloudant.ServerScope' incorrectly extends interface 'nano.ServerScope'.
  Types of property 'use' are incompatible.
    Type '(db: string) => DocumentScope<any>' is not assignable to type '<D>(db: string) => DocumentScope<D>'.
      Type 'DocumentScope<any>' is not assignable to type 'DocumentScope<D>'.
        Types of property 'partitionedListAsStream' are incompatible.
          Type '(partitionKey: string, params: DocumentFetchParams) => Request' is not assignable to type '(partitionKey: string, params?: DocumentFetchParams) => Request'.
            Type 'request.Request' is not assignable to type 'request.Request'. Two different types with this name exist, but they are unrelated.
              Types of property 'form' are incompatible.
                Type '{ (): FormData; (form: any): request.Request; }' is not assignable to type '{ (): FormData; (form: any): request.Request; }'. Two different types with this name exist, but they are unrelated.
                  Type 'FormData' is not assignable to type 'FormData'. Two different types with this name exist, but they are unrelated.
                    Property 'getBuffer' is missing in type 'FormData'.

109     interface ServerScope extends nano.ServerScope {
                  ~~~~~~~~~~~

types/index.d.ts:130:15 - error TS2430: Interface 'cloudant.DocumentScope<D>' incorrectly extends interface 'nano.DocumentScope<D>'.
  Types of property 'partitionedListAsStream' are incompatible.
    Type '(partitionKey: string, params: DocumentFetchParams) => Request' is not assignable to type '(partitionKey: string, params?: DocumentFetchParams) => Request'.
      Type 'request.Request' is not assignable to type 'request.Request'. Two different types with this name exist, but they are unrelated.

130     interface DocumentScope<D> extends nano.DocumentScope<D> {
                  ~~~~~~~~~~~~~

Approach

Pin to Nano ~8.1.0 patch versions.

Schema & API Changes

• "No change"

Security and Privacy

• "No change"

Testing

• N/A build or packaging only changes

Monitoring and Logging

• "No change"