Prepare to release v5.1.0 (#191)

## Problem

Prepare to release v5.1.0

## Solution

Update CHANGELOG.md and pineconeClientVersion in gradle.properties and
constants.java.

## 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

NA

Author: rohanshah18

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 [comment]: <> (When bumping [pc:VERSION_LATEST_RELEASE] create a new entry below)
 ### Unreleased version
+### 5.1.0
+- Add support for models api
+
 ### 5.0.0
 - Add support for backups and restore
 - Add support for list, describe, and delete namespaces

gradle.properties

@@ -1 +1 @@
-pineconeClientVersion = 5.0.0
+pineconeClientVersion = 5.1.0

src/main/java/io/pinecone/commons/Constants.java

@@ -1,5 +1,5 @@
 package io.pinecone.commons;
 
 public class Constants {
-    public static final String pineconeClientVersion = "v5.0.0";
+    public static final String pineconeClientVersion = "v5.1.0";
 }