Increment change_notes cache version for new server_id field in protobuf

Follow-up of Ic0e2cf4d8 introducing the server_id in the protobuf
definition of Change message and ChangeColumns, with the update of the
change_notes version number.

Release-Notes: Introduce server_id in change_notes cache and update its version number
Forward-Compatible: checked
Change-Id: I828d39c64d0265fd82aa42baf5713513cb1a3ff2
diff --git a/proto/entities.proto b/proto/entities.proto
index 9d4b394f..be04e97 100644
--- a/proto/entities.proto
+++ b/proto/entities.proto
@@ -31,7 +31,7 @@
 }
 
 // Serialized form of com.google.gerrit.entities.Change.
-// Next ID: 25
+// Next ID: 26
 message Change {
   required Change_Id change_id = 1;
   optional Change_Key change_key = 2;
@@ -50,6 +50,7 @@
   optional bool review_started = 22;
   optional Change_Id revert_of = 23;
   optional PatchSet_Id cherry_pick_of = 24;
+  optional string server_id = 25;
 
   // Deleted fields, should not be reused:
   reserved 3;    // row_version