Make SchemaVersion#guessVersion(Class) public again

This method was turned private by commit c4377cd3, but making it
private broke the delete-project plugin.

Change-Id: I7f1dbba1d53371599b48cf46ed0e3f60358060af
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaVersion.java b/gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaVersion.java
index 4e9e096..945baa8 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaVersion.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaVersion.java
@@ -46,7 +46,7 @@
     this.versionNbr = guessVersion(getClass());
   }
 
-  private static int guessVersion(Class<?> c) {
+  public static int guessVersion(Class<?> c) {
     String n = c.getName();
     n = n.substring(n.lastIndexOf('_') + 1);
     while (n.startsWith("0"))