Update MD051/link-fragments to not provide error context for multi-line scenarios.

test/snapshots/markdownlint-test-scenarios.js.md

@@ -23597,8 +23597,7 @@ Generated by [AVA](https://avajs.dev).
           ],
         },
         {
-          errorContext: `[Invalid {MD051}](#multi-line␊
-          "Title")`,
+          errorContext: null,
           errorDetail: null,
           errorRange: null,
           fixInfo: null,
@@ -23667,8 +23666,7 @@ Generated by [AVA](https://avajs.dev).
           ],
         },
         {
-          errorContext: `[Multi-line {MD051}](#NAMEDLINK␊
-          "Title")`,
+          errorContext: null,
           errorDetail: 'Expected: #namedlink; Actual: #NAMEDLINK',
           errorRange: null,
           fixInfo: null,