Fix location of repository analyzer API spec (#73378)

The repository analyzer API spec was incorrectly stored in the plugin
directory rather than in the main `rest-api-spec` directory. This commit
fixes that.

x-pack/plugin/snapshot-repo-test-kit/qa/rest/src/test/resources/rest-api-spec/api/snapshot.repository_analyze.json → rest-api-spec/src/main/resources/rest-api-spec/api/snapshot.repository_analyze.json

@@ -6,6 +6,11 @@
     },
     "stability":"stable",
     "visibility":"public",
+    "headers": {
+      "accept": [
+        "application/json"
+      ]
+    },
     "url":{
       "paths":[
         {