Fix typo in content-negociation.md
Fix typo in content-negociation.md

This broke the documentation.
teohhanhui/DunglasApiBundle,soyuka/core,lucascherifi/DunglasApiBundle,api-platform/core,soyuka/core,vincentchalamon/core,meyerbaptiste/core,meyerbaptiste/core,teohhanhui/api-platform-core,vincentchalamon/core,jdeniau/DunglasApiBundle,theofidry/DunglasApiBundle,leesiongchan/DunglasApiBundle,jdeniau/DunglasApiBundle,soyuka/core,jdeniau/DunglasApiBundle,teohhanhui/api-platform-core,ahlee2326/DunglasApiBundle,api-platform/core,meyerbaptiste/core,meyerbaptiste/core,api-platform/core,vincentchalamon/core,api-platform/core,teohhanhui/api-platform-core,vincentchalamon/core,soyuka/core,teohhanhui/api-platform-core,soyuka/DunglasApiBundle,jdeniau/DunglasApiBundle