Update Gentoo metadata

docs/packaging/linux-gentoo/metadata.xml

@@ -1,14 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE pkgmetadata SYSTEM "https://www.gentoo.org/dtd/metadata.dtd">
 <pkgmetadata>
-	<maintainer type="person" proxied="yes">
-		<email>mickael@apible.io</email>
-		<name>Mickaël Schoentgen</name>
-	</maintainer>
-	<maintainer type="project" proxied="proxy">
-		<email>proxy-maint@gentoo.org</email>
-		<name>Proxy Maintainers</name>
-	</maintainer>
+	<!-- maintainer-needed -->
 	<longdescription lang="en">
 		HTTPie (pronounced aitch-tee-tee-pie) is a command line HTTP
 		client. Its goal is to make CLI interaction with web services as