chore: fix links in README (#1646)

* Point to migrated java-shared-dependencies pom
* Add link to gapic-generator-java/DEVELOPMENT.md

Author: emmileaf

README.md

@@ -3,7 +3,7 @@
 This repository consists of the following modules:
 
 - **[gapic-generator-java](./gapic-generator-java/README.md)**: the Protobuf compiler plugin to generate Java code.
-  See [gapic-generator-java/DEVELOPMENT.md] for setup.
+  See [gapic-generator-java/DEVELOPMENT.md](./gapic-generator-java/README.md) for setup.
 - **[gax-java](./gax-java/README.md)**: the runtime library required for Google Cloud client libraries,
   including the ones generated by gapic-generator-java.
 - **[java-common-protos](./java-common-protos/README.md)** and **[api-common-java](./api-common-java/README.md)**: Protobuf-generated common
@@ -14,9 +14,8 @@ This repository consists of the following modules:
 - **[showcase](./showcase/README.md)**: demonstration of the generated client
   library for the fake "Showcase" API. 
 - **[gapic-generator-java-bom](./gapic-generator-java-bom)**: The Bill-of-Material for the libraries
-  produced from this repository. This is used by [google-cloud-java/java-shared-dependencies](
-  https://github.com/googleapis/google-cloud-java/blob/main/java-shared-dependencies/first-party-dependencies/pom.xml).
+  produced from this repository. This is used by [java-shared-dependencies](./java-shared-dependencies/first-party-dependencies/pom.xml).
 
 ## Development Setup
 
-See [DEVELOPMENT.md](DEVELOPMENT.md).
+See [DEVELOPMENT.md](DEVELOPMENT.md).