Remove lint for single_quotes, too much noise. (#78)

diff --git a/analysis_options.yaml b/analysis_options.yaml
index 5b5eb96..9d95259 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -32,6 +32,5 @@
     - only_throw_errors
     - prefer_final_fields
     - prefer_is_not_empty
-    - prefer_single_quotes
     - slash_for_doc_comments
     - type_init_formals