Remove absolute path to stylesheet.

Using an absolute path breaks the css resolution for a few reasons:

a) Locally it is missing because everything is copied into a temporary directory for processing. The temp directory
exists when the HTML is written out, but is removed once processing is done. The output is still referring to
the styles in the temp dir after processing is done.

b) When the HTML is deployed it will refer to the styles on the local directory that the docs were built. When other
users view it on the web server, the dir will not exist.

This commit removes the 'stylesheet' attribute definition to fix this.

spring-geode-docs/spring-geode-docs.gradle

@@ -17,8 +17,6 @@ dependencies {
 }
 
 def versions = dependencyManagement.managedVersions
-def relativePathToSpringCss = "css/spring.css"
-def absolutePathToSpringCss = new File(project.getBuildDir(), relativePathToSpringCss).getAbsolutePath()
 
 asciidoctor {
 
@@ -33,7 +31,6 @@ asciidoctor {
 		'download-url' : "${githubBaseUrl}/archive/${githubTag}.zip",
 		'github-url': githubUrl,
 		'github-samples-url': "${githubUrl}/spring-geode-samples",
-		'stylesheet' : absolutePathToSpringCss,
 		'highlightjsdir@': "js/highlight",
 		'docinfodir@': ".",
 		'master-apache-geode-version' : "19",