Bump spring.boot2.version from 2.7.18 to 4.0.0

Bumps `spring.boot2.version` from 2.7.18 to 4.0.0.

Updates `org.springframework.boot:spring-boot-maven-plugin` from 2.7.18 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.7.18...v4.0.0)

Updates `org.springframework.boot:spring-boot-starter-web` from 2.7.18 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.7.18...v4.0.0)

Updates `org.springframework.boot:spring-boot-starter-test` from 2.7.18 to 4.0.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.7.18...v4.0.0)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-maven-plugin
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- 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-test
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

openapi-generator-demo/pom.xml

@@ -87,7 +87,7 @@
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
-                <version>2.7.18</version>
+                <version>4.0.0</version>
             </plugin>
             <plugin>
                 <groupId>org.openapitools</groupId>

pom.xml

@@ -37,7 +37,7 @@
 
         <guava.mini.version>0.1.7</guava.mini.version>
         <jackson.version>2.20.1</jackson.version>
-        <spring.boot2.version>2.7.18</spring.boot2.version>
+        <spring.boot2.version>4.0.0</spring.boot2.version>
         <spring5.version>5.3.39</spring5.version>
         <spring.boot3.version>3.5.3</spring.boot3.version>
         <spring6.version>6.2.8</spring6.version>