Heroku ignores system.properties file and does not change jdk version

I'm trying to deploy jsp project on Heroku and I followed the guide https://devcenter.heroku.com/articles/java-webapp-runner#create-a-procfile. When I tried to deploy, Heroku used jdk 1.8 (i need 17 in my project). So I created a system.properties file with the line java.runtime.version=17, commited and pushed it to master, but Heroku still tries to use jdk 1.8. What am I doing wrong?

pom.xml:

    <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ruskaof</groupId>
    <artifactId>lab2WildFly</artifactId>
    <version>1.0-SNAPSHOT</version>
    <name>lab2WildFly</name>
    <packaging>war</packaging>

    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
            <dependency>
                <groupId>com.google.code.gson</groupId>
                <artifactId>gson</artifactId>
                <version>2.9.0</version>
            </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.3.1</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>17</source>
                    <target>17</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals><goal>copy</goal></goals>
                        <configuration>
                            <artifactItems>
                                <artifactItem>
                                    <groupId>com.heroku</groupId>
                                    <artifactId>webapp-runner</artifactId>
                                    <version>9.0.52.1</version>
                                    <destFileName>webapp-runner.jar</destFileName>
                                </artifactItem>
                            </artifactItems>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Procfile:

web: java $JAVA_OPTS -jar target/dependency/webapp-runner.jar --port $PORT target/*.war