Disable two lint rules which are being removed.

Each of these are going to be removed soon.

* avoid_null_checks_in_equality_operators
* unsafe_html

Work towards https://github.com/dart-lang/linter/issues/5063 and https://github.com/dart-lang/linter/issues/5001

analysis_options.yaml

@@ -56,7 +56,6 @@ linter:
     avoid_init_to_null: true
     avoid_js_rounded_ints: true
     avoid_multiple_declarations_per_line: true
-    avoid_null_checks_in_equality_operators: true
     avoid_positional_boolean_parameters: true
     avoid_print: true
     avoid_private_typedef_functions: true
@@ -220,7 +219,6 @@ linter:
     unnecessary_to_list_in_spreads: true
     unreachable_from_main: true
     unrelated_type_equality_checks: true
-    unsafe_html: true
     use_build_context_synchronously: true
     use_colored_box: true
     use_decorated_box: true