Remove unused setter

Author: fredericDelaporte

src/NHibernate/Cache/NonstrictReadWriteCache.cs

@@ -47,7 +47,6 @@ private CacheBase InternalCache
 					throw new InvalidOperationException(_isDestroyed ? "The cache has already been destroyed" : "The concrete cache is not defined");
 				return _cache;
 			}
-			set => _cache = value;
 		}
 
 		// 6.0 TODO: remove

src/NHibernate/Cache/ReadOnlyCache.cs

@@ -42,7 +42,6 @@ private CacheBase InternalCache
 					throw new InvalidOperationException(_isDestroyed ? "The cache has already been destroyed" : "The concrete cache is not defined");
 				return _cache;
 			}
-			set => _cache = value;
 		}
 
 		// 6.0 TODO: remove

src/NHibernate/Cache/ReadWriteCache.cs

@@ -66,7 +66,6 @@ private CacheBase InternalCache
 					throw new InvalidOperationException(_isDestroyed ? "The cache has already been destroyed" : "The concrete cache is not defined");
 				return _cache;
 			}
-			set => _cache = value;
 		}
 
 		// 6.0 TODO: remove