[BUG] Update developer guide on how to run spotless task on subprojects

[vrozov]

Describe the bug
Developer guide suggests to run ./gradlew server:spotlessJavaCheck as an example for executing it on subprojects, but spotless is not enabled for the server subproject, so it errors out:

FAILURE: Build failed with an exception.

* What went wrong:
Task 'spotlessJavaCheck' not found in project ':server'.

[owaiskazi19]

This is a meta issue to track spotless is enabled for all modules.

Owais

• :client:benchmark
• :client:client-benchmark-noop-api-plugin
• :client:rest
• :client:rest-high-level
• :client:sniffer
• :client:test
• :client:transport
• :example-plugins:custom-settings
• :example-plugins:custom-significance-heuristic
• :example-plugins:custom-suggester
• :example-plugins:painless-whitelist
• :example-plugins:rescore
• :example-plugins:rest-handler
• :example-plugins:script-expert-scoring

---

Owais

• :libs:opensearch-cli
• :libs:opensearch-core
• :libs:opensearch-dissect
• :libs:opensearch-geo
• :libs:opensearch-grok
• :libs:opensearch-nio
• :libs:opensearch-plugin-classloader
• :libs:opensearch-secure-sm
• :libs:opensearch-ssl-config
• :libs:opensearch-x-content

---

Owais

• :modules:aggs-matrix-stats
• :modules:analysis-common
• :modules:ingest-common
• :modules:ingest-geoip
• :modules:ingest-user-agent
• :modules:lang-expression
• :modules:lang-mustache
• :modules:lang-painless
• :modules:lang-painless:spi
• :modules:mapper-extras
• :modules:parent-join
• :modules:percolator
• :modules:rank-eval
• :modules:reindex
• :modules:repository-url
• :modules:systemd
• :modules:tasks
• :modules:transport-netty4

-- Himanshu

• :plugins:analysis-icu
• :plugins:analysis-kuromoji
• :plugins:analysis-nori
• :plugins:analysis-phonetic
• :plugins:analysis-smartcn
• :plugins:analysis-stempel
• :plugins:analysis-ukrainian
• :plugins:discovery-azure-classic
• :plugins:discovery-ec2
• :plugins:discovery-gce
• :plugins:ingest-attachment

---- Himanshu

• :plugins:mapper-annotated-text
• :plugins:mapper-murmur3
• :plugins:mapper-size
• :plugins:repository-azure
• :plugins:repository-gcs
• :plugins:repository-hdfs
• :plugins:repository-s3
• :plugins:store-smb
• :plugins:transport-nio
• :qa:die-with-dignity

--- Owais

• :rest-api-spec

--- Owais

• :server

---

Sarat

• :test:fixtures:azure-fixture
• :test:fixtures:gcs-fixture
• :test:fixtures:hdfs-fixture
• :test:fixtures:krb5kdc-fixture
• :test:fixtures:minio-fixture
• :test:fixtures:old-elasticsearch
• :test:fixtures:s3-fixture
• :test:framework
• :test:logger-usage