Remove broken customOperator test

The test's source snippet only declared struct Box with a custom
operator, but asserted on extractedTypes["AlwaysHere"] and
["OnlyWhenImportable"], which were never declared in that source -
copy-paste leftover from the neighboring canImport test.

Author: ktoso

Tests/SwiftExtractTests/AnalysisResultTests.swift

@@ -372,31 +372,6 @@ struct AnalysisResultSuite {
     #expect(result.extractedTypes["OnlyWhenImportable"] == nil)
   }
 
-  @Test func customOperator() throws {
-    var config = DefaultSwiftExtractConfiguration()
-    config.availableImportModules = ["MadeUpModule"]
-
-    let result = try analyze(
-      sources: [
-        (
-          "/fake/Source.swift",
-          """
-          struct Box {
-            static prefix func +++ (other: inout Box) -> Box {
-              return other
-            }
-          }
-          """
-        )
-      ],
-      moduleName: "Aquarium",
-      config: config
-    )
-
-    #expect(result.extractedTypes["AlwaysHere"] != nil)
-    #expect(result.extractedTypes["OnlyWhenImportable"] != nil)
-  }
-
   /// Adding the module to `availableImportModules` activates the
   /// `#if canImport(<module>)` clause so its declarations are extracted.
   @Test func availableImportModulesActivatesCanImportClause() throws {