Update flatpak manifest to use tagged release.

build-aux/com.saivert.pwvucontrol.json

@@ -63,7 +63,7 @@
             "sources" : [
                 {
                     "type" : "git",
-                    "branch": "main",
+                    "tag": "0.4.2",
                     "url" : "https://github.com/saivert/pwvucontrol.git"
                 }
             ]

data/com.saivert.pwvucontrol.metainfo.xml.in.in

@@ -3,8 +3,7 @@
 <component type="desktop-application">
   <id>@app-id@</id>
   <metadata_license>CC0</metadata_license>
-  <!-- Insert your license of choice here -->
-  <!-- <project_license>MIT</project_license> -->
+  <project_license>GPL-3.0-only</project_license>
   <name>pwvucontrol</name>
   <summary>Volume control for pipewire</summary>
   <description>
@@ -15,14 +14,22 @@
   </categories>
   <screenshots>
     <screenshot type="default">
-      <image>https://saivert.com/files/pwvucontrol%202023-07-26%2019-16-08.png</image>
+      <image>https://github.com/saivert/pwvucontrol/blob/0023790e57e1de5e3a65445cc0ce40be96477daf/screenshot.png</image>
       <caption>Main window</caption>
     </screenshot>
   </screenshots>
   <url type="homepage">https://github.com/saivert/pwvucontrol</url>
   <url type="bugtracker">https://github.com/saivert/pwvucontrol/issues</url>
   <content_rating type="oars-1.0" />
   <releases>
+    <release version="0.4.2" date="2023-12-21">
+      <description>
+        <p>Changelog since 0.3.1</p>
+        <ul>
+          <li>Added support for over-amplification. Enable via hamburger menu.</li>
+        </ul>
+      </description>
+    </release>
     <release version="0.3.1" date="2023-12-21">
       <description>
         <p>Changelog since 0.2.0</p>