Move FsVerityTest to presubmit as it's been stable

Remove "nextgen" since it's now redundant.

Bug: 296465999
Test: atest FsVerityTest
Change-Id: If441215692dc451d3633a4efb73cd61fb167ab24
diff --git a/tests/FsVerityTest/TEST_MAPPING b/tests/FsVerityTest/TEST_MAPPING
index 39944be..7d59d77 100644
--- a/tests/FsVerityTest/TEST_MAPPING
+++ b/tests/FsVerityTest/TEST_MAPPING
@@ -1,12 +1,7 @@
 {
-  "postsubmit": [
+  "presubmit": [
     {
       "name": "FsVerityTest"
-    },
-    // nextgen test only runs during postsubmit.
-    {
-      "name": "FsVerityTest",
-      "keywords": ["nextgen"]
     }
   ]
 }