[analyzer] Rename the element model migration guide.

The new name clarifies that the guide is specifically about element
model migration, not migration in general.

Changing the name now allows us to make links to the guide without
having to worry about updating those links if we change the name
later.

Change-Id: I6860867246b41671c20ecc725fdb2a5f7b77b949
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/419240
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/analyzer/doc/migration_guide.md b/pkg/analyzer/doc/element_model_migration_guide.md
similarity index 100%
rename from pkg/analyzer/doc/migration_guide.md
rename to pkg/analyzer/doc/element_model_migration_guide.md
diff --git a/pkg/analyzer/test/verify_docs_test.dart b/pkg/analyzer/test/verify_docs_test.dart
index 3a7bdde..d9a4d3b 100644
--- a/pkg/analyzer/test/verify_docs_test.dart
+++ b/pkg/analyzer/test/verify_docs_test.dart
@@ -60,8 +60,10 @@
   }
 
   Future<void> verifyFile(File file) async {
-    if (file.path.endsWith('/pkg/analyzer/doc/migration_guide.md') ||
-        file.path.endsWith(r'\pkg\analyzer\doc\migration_guide.md')) {
+    if (file.path
+            .endsWith('/pkg/analyzer/doc/element_model_migration_guide.md') ||
+        file.path
+            .endsWith(r'\pkg\analyzer\doc\element_model_migration_guide.md')) {
       return;
     }
     String content = file.readAsStringSync();