Remove support for non-generic collections

Src/FluentAssertions/AssertionExtensions.cs

@@ -277,16 +277,6 @@ public static NullableGuidAssertions Should(this Guid? actualValue)
             return new NullableGuidAssertions(actualValue);
         }
 
-        /// <summary>
-        /// Returns an <see cref="NonGenericCollectionAssertions"/> object that can be used to assert the
-        /// current <see cref="IEnumerable"/>.
-        /// </summary>
-        [Pure]
-        public static NonGenericCollectionAssertions Should(this IEnumerable actualValue)
-        {
-            return new NonGenericCollectionAssertions(actualValue);
-        }
-
         /// <summary>
         /// Returns an <see cref="GenericCollectionAssertions{T}"/> object that can be used to assert the
         /// current <see cref="IEnumerable{T}"/>.

Src/FluentAssertions/Collections/GenericDictionaryAssertions.cs

@@ -652,7 +652,7 @@ public AndConstraint<TAssertions> Contain(params KeyValuePair<TKey, TValue>[] ex
         /// <param name="becauseArgs">
         /// Zero or more objects to format using the placeholders in <paramref name="because" />.
         /// </param>
-        public AndConstraint<TAssertions> Contain(IEnumerable<KeyValuePair<TKey, TValue>> expected,
+        public new AndConstraint<TAssertions> Contain(IEnumerable<KeyValuePair<TKey, TValue>> expected,
             string because = "", params object[] becauseArgs)
         {
             Guard.ThrowIfArgumentIsNull(expected, nameof(expected), "Cannot compare dictionary with <null>.");
@@ -809,7 +809,7 @@ public AndConstraint<TAssertions> NotContain(params KeyValuePair<TKey, TValue>[]
         /// <param name="becauseArgs">
         /// Zero or more objects to format using the placeholders in <paramref name="because" />.
         /// </param>
-        public AndConstraint<TAssertions> NotContain(IEnumerable<KeyValuePair<TKey, TValue>> items,
+        public new AndConstraint<TAssertions> NotContain(IEnumerable<KeyValuePair<TKey, TValue>> items,
             string because = "", params object[] becauseArgs)
         {
             Guard.ThrowIfArgumentIsNull(items, nameof(items), "Cannot compare dictionary with <null>.");