Bump springBootVersion from 3.5.7 to 4.0.0

Bumps `springBootVersion` from 3.5.7 to 4.0.0.

Updates `org.springframework.boot:spring-boot-starter-web` from 3.5.7 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.5.7...v4.0.0)

Updates `org.springframework.boot:spring-boot-starter-actuator` from 3.5.7 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.5.7...v4.0.0)

Updates `org.springframework.boot:spring-boot-configuration-processor` from 3.5.7 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.5.7...v4.0.0)

Updates `org.springframework.boot:spring-boot-starter-test` from 3.5.7 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.5.7...v4.0.0)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-starter-web
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.springframework.boot:spring-boot-starter-actuator
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.springframework.boot:spring-boot-configuration-processor
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.springframework.boot:spring-boot-starter-test
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

build.gradle

@@ -19,7 +19,7 @@ group 'com.digitalsanctuary.cf.turnstile'
 description = 'SpringBoot Cloudflare Turnstile Library'
 
 ext {
-    springBootVersion = '3.5.7'
+    springBootVersion = '4.0.0'
     lombokVersion = '1.18.42'
 }