Fixed spacing in specs docs

Co-authored-by: Jeremie Vandenplas <[email protected]>

Author: ghbrown

doc/specs/stdlib_linalg.md

@@ -200,9 +200,9 @@ program demo_outer_product
     use stdlib_linalg, only: outer_product
     implicit none
     real, allocatable :: A(:,:), u(:), v(:)
-    u = [1. ,2. ,3. ]
+    u = [1., 2., 3. ]
     v = [3., 4.]
     A = outer_product(u,v)
     !A = reshape([3., 6., 9., 4., 8., 12.], [3,2])
 end program demo_outer_product
-```
+```