@Abhi_Tripathi ,@Srinivasa Reddy S :Thanks for your response.It was a typo mistake in  the code.I would like to send the email to the Account owner.When we use TemplateId ,TargetObjectId ...in doc it states that it should be of (a contact , lead or user) and toAddresses doesnot work when we use template id.

This is the complete Code :

global class  NotificationEmailtoOwner implements Database.Batchable < sObject >, Schedulable, Database.Stateful {
    global List<String> errorMessages = new List<String>();
    global Database.QueryLocator start(Database.BatchableContext bc) {
       
        Date ed = Date.today().addDays(110);
        System.debug(Date.today().addDays(110));
        
        set<Id> setContractIds = new set<Id>();

        for(Contract_role__c objContract: [SELECT  Contract__c FROM Contract_role__c WHERE Role__c = 'Subscription Administrator' AND Contract__r.EndDate =: ed]) {
            setContractIds.add(objContract.Contract__c);
        }
        
        return Database.getQueryLocator([Select  id, Contract_Name__c , EndDate ,Contact_Email__c, Contract_End_Date_2__c,  Account.Owner.Email,Account_Owner__c,ContractNumber,Contact__r.ID,Account_Owner_Email__c ,Account.ownerid FROM Contract  WHERE Id IN: setContractIds ]);
       
    }

    global void execute(Database.BatchableContext bc, List < Contract > recs) {
        List < Messaging.SingleEmailMessage > mailList = new List < Messaging.SingleEmailMessage > ();
        for (Contract c: recs) {
            if (c.Contact_Email__c != null) {
                List < String > toAddresses = new List < String > ();
                List < String > ccAddresses = new List < String > ();
                Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
               mail.setTargetObjectId(c.Account.OwnerID);
                 mail.setWhatId(c.Account.Owner.Email);
                 mail.setTemplateId('00X4B000000Dl3p');
                 mail.setSaveAsActivity(false);
                 mail.setSubject('Action Required - Renewal Alert Program Option');

                mailList.add(mail);
               
            }
        }
        Messaging.sendEmail(mailList);
    }

    global void finish(Database.BatchableContext bc) {
        AsyncApexJob aaj = [Select Id, Status, NumberOfErrors, JobItemsProcessed, MethodName, TotalJobItems, CreatedBy.Email from AsyncApexJob where Id =:BC.getJobId()];
        
        // Send an email to the Apex job's submitter notifying of job completion.
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        String[] toAddresses = new String[] {aaj.CreatedBy.Email};
        mail.setToAddresses(toAddresses);
       // mail.setccAddresses(CCAddresses);
        mail.setSubject('JOB Salesforce NotificationEmailtoOwner Finished: ' + aaj.Status);
        String bodyText='Total Job Items ' + aaj.TotalJobItems + ' Number of records processed ' + aaj.JobItemsProcessed + ' with '+ aaj.NumberOfErrors + ' failures.\n';
        bodyText += 'Number of Error Messages ' + errorMessages.size() + '\n';
        bodyText += 'Error Message' + String.join(errorMessages, '\n');
        mail.setPlainTextBody(bodyText);
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
    }
    
    global void execute(SchedulableContext SC) {
         NotificationEmailtoOwner batchable = new  NotificationEmailtoOwner();
        database.executebatch(batchable);
    }
}

When i execute the code ,the Account owner is not recevining any email.But my goal is to send an email to the Account owner.The code is correct or is that something im missing out .Any help very much appreciated.