Update version for release.

runtime/Info.plist

@@ -8,9 +8,9 @@
     <key>CFBundleName</key>
     <string>pgAdmin 4</string>
     <key>CFBundleShortVersionString</key>
-    <string>4.19.0</string>
+    <string>4.20.0</string>
     <key>CFBundleVersion</key>
-    <string>4.19.0</string>
+    <string>4.20.0</string>
     <key>LSMinimumSystemVersion</key>
     <string>10.10</string>
     <key>NSHumanReadableCopyright</key>

runtime/pgAdmin4.pro

@@ -1,4 +1,4 @@
-VERSION = 4.19.0.0
+VERSION = 4.20.0.0
 QMAKE_TARGET_COMPANY = "The pgAdmin Development Team"
 QMAKE_TARGET_PRODUCT = "pgAdmin 4"
 QMAKE_TARGET_DESCRIPTION = "pgAdmin 4 Desktop Runtime"