Remove unused playbooks

We no longer use the local or per branch playbooks. Instead we can flex
the build using the same env variables that the partial build leverages
& fixed playbooks in each branch.

lib/antora/templates/per-branch-antora-playbook.yml

@@ -1,37 +0,0 @@
-# The purpose of this Antora playbook is to build the docs in the current branch.
-antora:
-  extensions:
-  - '@antora/collector-extension'
-  - id: '@antora/atlas-extension'
-    require: '@antora/atlas-extension'
-    enabled: false
-  - '@opendevise/antora-release-line-extension'
-  - require: '@springio/antora-extensions/tabs-migration-extension'
-    unwrap_example_block: always
-site:
-  title: Spring Security Reference
-content:
-  sources:
-  - url: ./..
-    branches: HEAD
-    start_path: docs
-    worktrees: true
-asciidoc:
-  attributes:
-    page-stackoverflow-url: https://stackoverflow.com/tags/spring-security
-    hide-uri-scheme: '@'
-    page-pagination: ''
-    primary-site-url: https://docs.spring.io/spring-security/reference
-    tabs-sync-option: '@'
-  extensions:
-  - '@asciidoctor/tabs'
-  sourcemap: true
-urls:
-  latest_version_segment: ''
-runtime:
-  log:
-    failure_level: warn
-ui:
-  bundle:
-    url: https://github.com/spring-io/antora-ui-spring/releases/download/v0.3.6/ui-bundle.zip
-    snapshot: true

local-antora-playbook.yml

@@ -1,34 +0,0 @@
-antora:
-  extensions:
-  - ./lib/antora/extensions/inject-collector-config.js
-  - '@antora/collector-extension'
-  - ./lib/antora/extensions/version-fix.js
-  - '@opendevise/antora-release-line-extension'
-  - require: '@springio/antora-extensions/tabs-migration-extension'
-    # uncomment this option to save the migrated content to the worktree
-    #save_result: true
-    unwrap_example_block: always
-site:
-  title: Spring Security
-  url: https://docs.spring.io/spring-security/reference
-content:
-  sources:
-  - url: .
-    branches: [main, '5.{{6..9},{1..9}+({0..9})}.x', '6.+({0..9}).x']
-    worktrees: true # automatically discovers worktrees, if present; otherwise, will use git tree
-    tags: ['5.{{6..9},{1..9}+({0..9})}.+({0..9})?(-RC+({0..9}))', '6.+({0..9}).+({0..9})?(-{RC,M}*)']
-    start_path: docs
-asciidoc:
-  attributes:
-    page-pagination: ''
-    hide-uri-scheme: '@'
-    tabs-sync-option: '@'
-  extensions:
-  - '@asciidoctor/tabs'
-  - '@springio/asciidoctor-extensions'
-urls:
-  latest_version_segment: ''
-ui:
-  bundle:
-    url: https://github.com/spring-io/antora-ui-spring/releases/download/latest/ui-bundle.zip
-    snapshot: true