Removing old/deprecated API specs and updating README file (#40)

Co-authored-by: Sujit Gadkari <sgadkari@paypal.com>

Author: SujitGadkari

README.md

@@ -51,15 +51,11 @@ The [OpenAPI](https://swagger.io/specification/v3/) specification is a programmi
 | Add Tracking          | v1      | [OpenAPI](./openapi/shipping_shipment_tracking_v1.json), [API Reference](https://developer.paypal.com/docs/api/tracking/v1/)                           |
 | Catalog Products      | v1      | [OpenAPI](./openapi/catalogs_products_v1.json), [API Reference](https://developer.paypal.com/docs/api/catalog-products/v1/)                            |
 | Disputes              | v1      | [OpenAPI](./openapi/customer_disputes_v1.json), [API Reference](https://developer.paypal.com/docs/api/customer-disputes/v1/)                           |
-| Invoices              | v1      | [OpenAPI](./openapi/invoicing_v1.json), [API Reference](https://developer.paypal.com/docs/api/invoicing/v1/)                                           |
 | Invoices              | v2      | [OpenAPI](./openapi/invoicing_v2.json), [API Reference](https://developer.paypal.com/docs/api/invoicing/v2/)                                           |
-| Orders                | v1      | [OpenAPI](./openapi/checkout_orders_v1.json), [API Reference](https://developer.paypal.com/docs/api/orders/v1/)                                        |
 | Orders                | v2      | [OpenAPI](./openapi/checkout_orders_v2.json), [API Reference](https://developer.paypal.com/docs/api/orders/v2/)                                        |
-| Partner Referrals     | v1      | [OpenAPI](./openapi/customer_partner_referrals_v1.json), [API Reference](https://developer.paypal.com/docs/api/partner-referrals/v1/)                  |
 | Partner Referrals     | v2      | [OpenAPI](./openapi/customer_partner_referrals_v2.json), [API Reference](https://developer.paypal.com/docs/api/partner-referrals/v2/)                  |
 | Payment Experience    | v1      | [OpenAPI](./openapi/payment-experience_web_experience_profiles_v1.json), [API Reference](https://developer.paypal.com/docs/api/payment-experience/v1/) |
 | Payment Method Tokens | v3      | [OpenAPI](./openapi/vault_payment_tokens_v3.json), [API Reference](https://developer.paypal.com/docs/api/payment-tokens/v3/)                           |
-| Payments              | v1      | [OpenAPI](./openapi/payments_payment_v1.json), [API Reference](https://developer.paypal.com/docs/api/payments/v1/)                                     |
 | Payments              | v2      | [OpenAPI](./openapi/payments_payment_v2.json), [API Reference](https://developer.paypal.com/docs/api/payments/v2/)                                     |
 | Payouts               | v1      | [OpenAPI](./openapi/payments_payouts_batch_v1.json), [API Reference](https://developer.paypal.com/docs/api/payments.payouts-batch/v1/)                 |
 | Subscriptions         | v1      | [OpenAPI](./openapi/billing_subscriptions_v1.json), [API Reference](https://developer.paypal.com/docs/api/subscriptions/v1/)                           |