updater: Bump up the BBOTA version to 4.

To accommodate new changes in N release, such as error correction [1]
and other potential changes to the updater.

[1]: commit 0a7b47397d

Change-Id: I4dd44417d07dd0a31729894628635a0aa1659008

updater/blockimg.cpp

@@ -1374,7 +1374,7 @@ static Value* PerformBlockImageUpdate(const char* name, State* state, int /* arg
     std::vector<std::string> lines = android::base::Split(transfer_list, "\n");
 
     // First line in transfer list is the version number
-    if (!android::base::ParseInt(lines[0].c_str(), &params.version, 1, 3)) {
+    if (!android::base::ParseInt(lines[0].c_str(), &params.version, 1, 4)) {
         fprintf(stderr, "unexpected transfer list version [%s]\n", lines[0].c_str());
         return StringValue(strdup(""));
     }