Remove release date from new releases and add 2.0.0-rc1

With the ASF donation we no longer have the ability to specify an exact release date due to the voting process. For this reason we will stop including a release date on the changelog.

This patch also makes it clear what changes were released in 2.0.0-rc1 so that users can know what is different between rc1 and GA.

Patch by João Reis; reviewed by TBD for CASSGO-86

Author: joao-r-reis

CHANGELOG.md

@@ -5,10 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [2.0.0] - Unreleased
+## [2.0.0]
 
 ### Removed
 
+#### 2.0.0-rc1
+
 - Drop support for old CQL protocol versions: 1 and 2 (CASSGO-75)
 - Cleanup of deprecated elements (CASSGO-12)
 - Remove global NewBatch function (CASSGO-15)
@@ -17,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+#### 2.0.0-rc1
+
 - Support vector type (CASSGO-11)
 - Allow SERIAL and LOCAL_SERIAL on SELECT statements (CASSGO-26)
 - Support of sending queries to the specific node with Query.SetHostID() (CASSGO-4)
@@ -29,6 +33,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+#### 2.0.0
+
+- Remove release date from changelog and add 2.0.0-rc1 (CASSGO-86)
+
+#### 2.0.0-rc1
+
 - Moved the Snappy compressor into its own separate package (CASSGO-33)
 - Move lz4 compressor to lz4 package within the gocql module (CASSGO-32)
 - Don't restrict server authenticator unless PasswordAuthentictor.AllowedAuthenticators is provided (CASSGO-19)
@@ -55,6 +65,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+#### 2.0.0-rc1
+
 - Cassandra version unmarshal fix (CASSGO-49)
 - Retry policy now takes into account query idempotency (CASSGO-27)
 - Don't return error to caller with RetryType Ignore (CASSGO-28)