Remove deprecated experimental invariant_booleans lint rule (dart-lang/sse#61)

diff --git a/pkgs/sse/analysis_options.yaml b/pkgs/sse/analysis_options.yaml
index f767506..1f65ccf 100644
--- a/pkgs/sse/analysis_options.yaml
+++ b/pkgs/sse/analysis_options.yaml
@@ -36,7 +36,6 @@
     - empty_statements
     - hash_and_equals
     - implementation_imports
-    - invariant_booleans
     - iterable_contains_unrelated_type
     - library_names
     - library_prefixes