Antora build failures

[mp911de]

Antora build on main and 6.0.x fails with:

[INFO] [INFO] 17 goals, 17 executed
[INFO] [14:22:43.904] WARN (asciidoctor): unterminated tabs block
[INFO]     file: src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc:466
[INFO]     source: https://github.com/spring-projects/spring-data-elasticsearch (branch: main | start path: src/main/antora)
[INFO] [14:22:43.908] WARN (asciidoctor): unterminated example block
[INFO]     file: src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc:488
[INFO]     source: https://github.com/spring-projects/spring-data-elasticsearch (branch: main | start path: src/main/antora)
[INFO] [14:22:44.467] WARN (asciidoctor): unterminated tabs block
[INFO]     file: src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc:466
[INFO]     source: https://github.com/spring-projects/spring-data-elasticsearch (branch: 6.0.x | start path: src/main/antora)
[INFO] [14:22:44.469] WARN (asciidoctor): unterminated example block
[INFO]     file: src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc:488
[INFO]     source: https://github.com/spring-projects/spring-data-elasticsearch (branch: 6.0.x | start path: src/main/antora)
[INFO] [14:22:44.966] WARN (asciidoctor): unterminated tabs block
[INFO]     file: src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc:466
[INFO]     source: https://github.com/spring-projects/spring-data-elasticsearch (tag: 6.0.0 | start path: src/main/antora)
[INFO] [14:22:44.968] WARN (asciidoctor): unterminated example block
[INFO]     file: src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc:488
[INFO]     source: https://github.com/spring-projects/spring-data-elasticsearch (tag: 6.0.0 | start path: src/main/antora)

[sothawo]

backported to 6.0.x as well