Deprecate Probability field on Opportunity (#6207)

Closes #5735.
The field probability on opportunity will -
- stop being created for new workspaces (after this PR is merged)
- have "isCustom" value set to true and be displayed as such in the
settings (after this PR is merged + sync-metadata is run on workspace)
- still show in the views (all the time)

This field is deprecated as a standard field but not replaced by another
one, so we are not adding the `(deprecated)` suffix in the label.

packages/twenty-front/src/modules/object-metadata/utils/getObjectMetadataItemsMock.ts

@@ -466,23 +466,6 @@ export const getObjectMetadataItemsMock = () => {
           fromRelationMetadata: null,
           toRelationMetadata: null,
         },
-        {
-          __typename: 'field',
-          id: '20202020-3b9c-4e58-a3d2-c617d3b596b1',
-          type: 'TEXT',
-          name: 'probability',
-          label: 'Probability',
-          description: 'Opportunity probability',
-          icon: 'IconProgressCheck',
-          isCustom: false,
-          isActive: true,
-          isSystem: false,
-          isNullable: true,
-          createdAt: '2023-11-30T11:13:15.308Z',
-          updatedAt: '2023-11-30T11:13:15.308Z',
-          fromRelationMetadata: null,
-          toRelationMetadata: null,
-        },
         {
           __typename: 'fieldEdge',
           node: {