Update vertexai changelog file (#6352)

It includes the full list of changes since the last release.

---------

Co-authored-by: rachelsaunders <[email protected]>

Author: rlazo

firebase-vertexai/CHANGELOG.md

@@ -1,5 +1,21 @@
 # Unreleased
-* [changed] Breaking Change: refactored enum classes to be normal classes (#6340). 
+* [feature] Added support for `title` and `publicationDate` in citations. (#6309)
+* [feature] Added support for `frequencyPenalty`, `presencePenalty`, and `HarmBlockMethod`. (#6309)
+* [changed] **Breaking Change**: Introduced `Citations` class. Now `CitationMetadata` wraps that type. (#6276)
+* [changed] **Breaking Change**: Introduced `FunctionCall` and `FunctionResponse` types. Now `FunctionCallPart` and `FunctionResponsePart` wrap those types, respectively. (#6311)
+* [changed] **Breaking Change**: Reworked `Schema` declaration mechanism. (#6258)
+* [changed] **Breaking Change**: Reworked function calling mechanism to use the new `Schema` format. Function calls no longer use native types, nor include references to the actual executable code. (#6258)
+* [changed] **Breaking Change**: Made `totalBillableCharacters` field in `CountTokens` nullable and optional. (#6294)
+* [changed] **Breaking Change**: Removed `UNKNOWN` option for the `HarmBlockThreshold` enum. (#6294)
+* [changed] **Breaking Change**: Removed `UNSPECIFIED` option for the `HarmBlockThreshold`, `HarmProbability`, `HarmSeverity`, and `BlockReason` enums. (#6294)
+* [changed] **Breaking Change**: Renamed `BlockThreshold` as `HarmBlockThreshold`. (#6262)
+* [changed] **Breaking Change**: Renamed all types and methods starting with `blob` to start with `inlineData`. (#6309)
+* [changed] **Breaking Change**: Changed the order of arguments in `InlineDataPart` to match `ImagePart`. (#6340)
+* [changed] **Breaking Change**: Changed `RequestOption` to accept only `long` timeout values. (#6289)
+* [changed] **Breaking Change**: Moved `requestOptions` to the last positional argument in the `generativeModel` argument list. (#6292)
+* [changed] **Breaking Change**: Replaced sealed classes with abstract classes for `StringFormat`. (#6334)
+* [changed] **Breaking Change**: Refactored enum classes to be normal classes. (#6340)
+* [changed] **Breaking Change**: Marked `GenerativeModel` properties as private. (#6309)
 
 
 # 16.0.0-beta05
@@ -17,4 +33,3 @@
 * [feature] Added support for `responseMimeType` in `GenerationConfig`.
 * [changed] Renamed `GoogleGenerativeAIException` to `FirebaseVertexAIException`.
 * [changed] Updated the KDocs for various classes and functions.
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