chore(build): remove openapi generator (#683)

Remove unused OpenAPI Generator plugin, its configuration, and the
`.openapi-generator-ignore` file.

## Breaking Changes
none

## Types of changes
- [ ] 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 change)
- [ ] Documentation update

## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

gradle/libs.versions.toml

@@ -10,7 +10,6 @@ ktlint = "14.2.0"
 knit = "0.5.1"
 mavenPublish = "0.36.0"
 netty = "4.2.12.Final"
-openapi-generator = "7.21.0"
 
 # libraries version
 awaitility = "4.3.0"
@@ -81,4 +80,3 @@ kotlinx-binary-compatibility-validator = { id = "org.jetbrains.kotlinx.binary-co
 kover = { id = "org.jetbrains.kotlinx.kover", version.ref = "kover" }
 ktlint = { id = "org.jlleitschuh.gradle.ktlint", version.ref = "ktlint" }
 knit = { id = "org.jetbrains.kotlinx.knit", version.ref = "knit" }
-openapi-generator = { id = "org.openapi.generator", version.ref = "openapi-generator" }