[Security Solution][Serverless] Fix project features url (elastic#181608

)

## Summary

Fixes the double slash (`//`) in the URL to manage the serverless
project features from the Get Started page:

before:

`https://console.qa.cld.elstc.co/projects//security/:id`

<img width="1207" alt="before"
src="https://github.com/elastic/kibana/assets/17747913/10dc4a4f-99b4-4ce8-abc8-858fa1e95236">

After:

`https://console.qa.cld.elstc.co/projects/security/:id`

<img width="1207" alt="after"
src="https://github.com/elastic/kibana/assets/17747913/936bcffb-4530-4a9d-90db-b4a5c4f9f1cd">

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

x-pack/plugins/security_solution_serverless/public/navigation/util.test.ts

@@ -12,7 +12,7 @@ const cloud = {
   serverless: {
     projectId: '1234',
   },
-  projectsUrl: 'https://cloud.elastic.co/projects',
+  projectsUrl: 'https://cloud.elastic.co/projects/',
 } as CloudStart;
 
 describe('util', () => {
@@ -29,7 +29,7 @@ describe('util', () => {
 
     it('should return the correct url', () => {
       expect(getProjectFeaturesUrl(cloud)).toBe(
-        `${cloud.projectsUrl}/security/${cloud.serverless?.projectId}?open=securityProjectFeatures`
+        `${cloud.projectsUrl}security/${cloud.serverless?.projectId}?open=securityProjectFeatures`
       );
     });
   });

x-pack/plugins/security_solution_serverless/public/navigation/util.ts

@@ -20,7 +20,7 @@ export const getProjectFeaturesUrl = (cloud: CloudStart): string | undefined =>
   if (!projectsBaseUrl || !projectId) {
     return undefined;
   }
-  return `${projectsBaseUrl}/${SECURITY_PROJECT_TYPE}/${projectId}?open=securityProjectFeatures`;
+  return `${projectsBaseUrl}${SECURITY_PROJECT_TYPE}/${projectId}?open=securityProjectFeatures`;
 };
 
 export const getCloudUrl: GetCloudUrl = (cloudUrlKey, cloud) => {