Issue 26050. Don't suggest to import an already imported (with 'show') library again.

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index dbf0da7302499f9c0bfd9712fa1ce8e9449a98cd..6c3a1e6e9f1d4e526eb0b7cadab4c9992b70cf6a 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -1494,6 +1494,10 @@ class FixProcessor {
         String libraryUri = sdkLibrary.shortName;
         Source librarySource =
             sdkSourceFactory.resolveUri(unitSource, libraryUri);
+        // maybe already imported
+        if (alreadyImportedWithPrefix.contains(librarySource)) {
+          continue;
+        }
         // prepare LibraryElement
         LibraryElement libraryElement =
             context.getResult(librarySource, LIBRARY_ELEMENT1);
@@ -1523,7 +1527,7 @@ class FixProcessor {
         if (librarySource.isInSystemLibrary) {
           continue;
         }
-        // maybe already imported with a prefix
+        // maybe already imported
         if (alreadyImportedWithPrefix.contains(librarySource)) {
           continue;
         }