chore(deps-dev): bump fetch-mock from 11.1.5 to 12.6.0 in /superset-frontend/packages/superset-ui-core (#36662)

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Signed-off-by: hainenber <dotronghai96@gmail.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Evan Rusackas <evan@rusackas.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: hainenber <dotronghai96@gmail.com>

superset-frontend/src/explore/components/ExploreChartHeader/ExploreChartHeader.test.tsx

@@ -144,9 +144,6 @@ const createProps = (additionalProps = {}) => ({
 fetchMock.post(
   'http://api/v1/chart/data?form_data=%7B%22slice_id%22%3A318%7D',
   { body: {} },
-  {
-    sendAsJson: false,
-  },
 );
 // eslint-disable-next-line no-restricted-globals -- TODO: Migrate from describe blocks
 describe('ExploreChartHeader', () => {