Change "client" to "SDK" (#64)

## Problem

We are inconsistent in how we refer to our client libraries.

## Solution

As we mostly refer to our "SDKs" rather than our "clients", we've
updated our docs to prefer "SDK". This PR makes equivalent updates to
the Go SDK README.

Addresses: https://app.asana.com/0/1206419570114940/1207978475519546/f

## Type of Change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update
- [ ] Infrastructure change (CI configs, etc)
- [x] Non-code change (docs, etc)
- [ ] None of the above: (explain here)

## Test Plan

Describe specific steps for validating this change.

README.md

@@ -1,6 +1,6 @@
-# Pinecone Go Client · ![License](https://img.shields.io/github/license/pinecone-io/go-pinecone?color=orange) [![Go Reference](https://pkg.go.dev/badge/github.com/pinecone-io/go-pinecone.svg)](https://pkg.go.dev/github.com/pinecone-io/go-pinecone@main/pinecone) [![Go Report Card](https://goreportcard.com/badge/github.com/pinecone-io/go-pinecone)](https://goreportcard.com/report/github.com/pinecone-io/go-pinecone)
+# Pinecone Go SDK · ![License](https://img.shields.io/github/license/pinecone-io/go-pinecone?color=orange) [![Go Reference](https://pkg.go.dev/badge/github.com/pinecone-io/go-pinecone.svg)](https://pkg.go.dev/github.com/pinecone-io/go-pinecone@main/pinecone) [![Go Report Card](https://goreportcard.com/badge/github.com/pinecone-io/go-pinecone)](https://goreportcard.com/report/github.com/pinecone-io/go-pinecone)
 
-This is the official Go client for [Pinecone](https://www.pinecone.io).
+This is the official Go SDK for [Pinecone](https://www.pinecone.io).
 
 ## Documentation
 
@@ -19,9 +19,9 @@ go-pinecone contains
 
 See the [Pinecone API Docs](https://docs.pinecone.io/reference/) for more information.
 
-## Upgrading your client
+## Upgrading the SDK
 
-To upgrade your client to the latest version, run:
+To upgrade the SDK to the latest version, run:
 
 ```shell
 go get -u github.com/pinecone-io/go-pinecone/pinecone@latest
@@ -33,7 +33,7 @@ go get -u github.com/pinecone-io/go-pinecone/pinecone@latest
 
 ## Installation
 
-To install the Pinecone Go client, run the following in your terminal:
+To install the Pinecone Go SDK, run the following in your terminal:
 
 ```shell
 go get github.com/pinecone-io/go-pinecone/pinecone