Remove documentation for unsupported cases

Turns out the `case` keyword does some extra magic that isn't trivially 
implemented.

src/spectator/dsl/matcher_dsl.cr

@@ -23,12 +23,8 @@ module Spectator::DSL
     # ```
     # expect(1 + 2).to be(3)
     # expect(5).to be(Int32) # Using `#be_a` instead is recommened here.
-    # expect(5).to be(.odd?) # Using `#be_odd` instead is recommended here.
     # expect(tuple).to be({1, 2})
     # ```
-    #
-    # See https://crystal-lang.org/reference/syntax_and_semantics/case.html
-    # for more examples of what could be used here.
     macro be(expected)
       ::Spectator::Matchers::CaseMatcher.new({{expected.stringify}}, {{expected}})
     end