Bump com.squareup.okhttp3:okhttp-bom

Bumps [com.squareup.okhttp3:okhttp-bom](https://github.com/square/okhttp) from 5.0.0-alpha.11 to 5.0.0-alpha.12.
- [Changelog](https://github.com/square/okhttp/blob/master/CHANGELOG.md)
- [Commits](square/okhttp@jesse-5.0.0-alpha.11...parent-5.0.0-alpha.12)

---
updated-dependencies:
- dependency-name: com.squareup.okhttp3:okhttp-bom
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

starters/okhttp5/build.gradle

@@ -5,7 +5,7 @@ description = "OkHttp 5 Spring Boot Starter"
 
 dependencies {
     api platform(project(":dependencies"))
-    api platform('com.squareup.okhttp3:okhttp-bom:5.0.0-alpha.11')
+    api platform('com.squareup.okhttp3:okhttp-bom:5.0.0-alpha.12')
     api 'org.springframework.boot:spring-boot-starter'
     api project(':autoconfigure')
     api 'com.squareup.okhttp3:okhttp'