DAS: Remove unused createAnalysisOptionsFile

Change-Id: I03a452d6b93d2d25e1da9cabc1c120ebe468562d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/216501
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>

pkg/analysis_server/test/analysis/get_hover_test.dart

@@ -868,7 +868,6 @@ void f() {
   }
 
   Future<void> test_nonNullable() async {
-    createAnalysisOptionsFile(experiments: ['non-nullable']);
     addTestFile('''
 int? f(double? a) => null;
 

pkg/analysis_server/test/analysis_abstract.dart

@@ -89,19 +89,6 @@ class AbstractAnalysisTest with ResourceProviderMixin {
     return testFile;
   }
 
-  /// Create an analysis options file based on the given arguments.
-  void createAnalysisOptionsFile({List<String>? experiments}) {
-    var buffer = StringBuffer();
-    if (experiments != null) {
-      buffer.writeln('analyzer:');
-      buffer.writeln('  enable-experiment:');
-      for (var experiment in experiments) {
-        buffer.writeln('    - $experiment');
-      }
-    }
-    newAnalysisOptionsYamlFile(projectPath, content: buffer.toString());
-  }
-
   AnalysisServer createAnalysisServer() {
     //
     // Create an SDK in the mock file system.