Write CSS file as UTF-8

By not using deprecated IOUtils method.

Change-Id: Id9b61b089b719c03da298e03b4df541b0dd17c3d
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.images/+/190611
Reviewed-by: Matthias Becker <ma.becker@sap.com>
Reviewed-by: Alexander Kurtakov <akurtako@redhat.com>
Tested-by: Alexander Kurtakov <akurtako@redhat.com>

org.eclipse.images.renderer/src/main/java/org/eclipse/images/renderer/ExtractCSSMojo.java

diff --git a/org.eclipse.images.renderer/src/main/java/org/eclipse/images/renderer/ExtractCSSMojo.java b/org.eclipse.images.renderer/src/main/java/org/eclipse/images/renderer/ExtractCSSMojo.java
index 2e38dfa..7662bb6 100644
--- a/org.eclipse.images.renderer/src/main/java/org/eclipse/images/renderer/ExtractCSSMojo.java
+++ b/org.eclipse.images.renderer/src/main/java/org/eclipse/images/renderer/ExtractCSSMojo.java
@@ -18,6 +18,7 @@
 import java.io.StringWriter;
 import java.io.Writer;
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -174,7 +175,7 @@
 
 			log.info("Creating css for: " + css);
 			
-			IOUtils.write(stream.toString(), new FileOutputStream(newOutput));
+			IOUtils.write(stream.toString(), new FileOutputStream(newOutput), StandardCharsets.UTF_8);
 		} catch (Exception e) {
 			log.error("Error creating CSS: " + e.getMessage(), e);
 		}