Improve restricted environment config for devfiles

plugins {
	id 'org.springframework.boot' version '2.2.2.RELEASE'
	id 'io.spring.dependency-management' version '1.0.8.RELEASE'
	id 'java'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
	mavenCentral()
}

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
	implementation 'org.springframework.boot:spring-boot-starter-web'
	testImplementation('org.springframework.boot:spring-boot-starter-test') {
		exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
	}
}

test {
	useJUnitPlatform()
}

Could not run phased build action using Gradle installation '/opt/gradle'.
Build file '/projects/gs-validating-form-input/complete/build.gradle' line: 2
Plugin [id: 'org.springframework.boot', version: '2.2.2.RELEASE'] was not found in any of the following sources:
- Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
- Plugin Repositories (could not resolve plugin artifact 'org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.2.RELEASE')
  Searched in the following repositories:
    Gradle Central Plugin Repository
Plugin [id: 'org.springframework.boot', version: '2.2.2.RELEASE'] was not found in any of the following sources:
- Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
- Plugin Repositories (could not resolve plugin artifact 'org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.2.RELEASE')
  Searched in the following repositories:
    Gradle Central Plugin RepositoryJava(0)