docs: fix docs for MMatrix and SMatrix macro (#1040)

Author: nhz2

src/MMatrix.jl

@@ -36,7 +36,7 @@ end
     @MMatrix [a b c d]
     @MMatrix [[a, b];[c, d]]
     @MMatrix [i+j for i in 1:2, j in 1:2]
-    @MMatrix ones(2, 2, 2)
+    @MMatrix ones(2, 2)
 
 A convenience macro to construct `MMatrix`.
 See [`@SArray`](@ref) for detailed features.

src/SMatrix.jl

@@ -111,7 +111,7 @@ end
     @SMatrix [a b c d]
     @SMatrix [[a, b];[c, d]]
     @SMatrix [i+j for i in 1:2, j in 1:2]
-    @SMatrix ones(2, 2, 2)
+    @SMatrix ones(2, 2)
 
 A convenience macro to construct `SMatrix`.
 See [`@SArray`](@ref) for detailed features.