fix: Do not use npm install from maven but as prerequisite

asciidoctor-stylesheet/pom.xml

@@ -7,8 +7,6 @@
   <packaging>pom</packaging>
 
   <properties>
-    <node.version>v10.16.2</node.version>
-    <npm.version>6.9.0</npm.version>
     <frontend-maven-plugin.version>1.6</frontend-maven-plugin.version>
     <stylesheet.build.dir>${basedir}/stylesheets/</stylesheet.build.dir>
     <stylesheet.target.dir>${project.build.directory}/stylesheets/</stylesheet.target.dir>
@@ -44,36 +42,6 @@
 
   <build>
     <plugins>
-      <plugin>
-        <groupId>com.github.eirslett</groupId>
-        <artifactId>frontend-maven-plugin</artifactId>
-        <version>${frontend-maven-plugin.version}</version>
-        <configuration>
-          <workingDirectory>./</workingDirectory>
-        </configuration>
-        <executions>
-          <execution>
-            <id>install node and npm</id>
-            <goals>
-              <goal>install-node-and-npm</goal>
-            </goals>
-            <configuration>
-              <nodeVersion>${node.version}</nodeVersion>
-              <npmVersion>${npm.version}</npmVersion>
-            </configuration>
-          </execution>
-          <execution>
-            <id>npm install</id>
-            <goals>
-              <goal>npm</goal>
-            </goals>
-            <configuration>
-              <arguments>install</arguments>
-            </configuration>
-          </execution>
-        </executions>
-      </plugin>
-
       <plugin>
         <groupId>de.saumya.mojo</groupId>
         <artifactId>gem-maven-plugin</artifactId>