test: fix fixtures by adding context

Signed-off-by: Shingo OKAWA <shingo.okawa.g.h.c@gmail.com>

Author: ognis1205

.github/fixtures/test-from-context-does-not-discard-fields/context.json

@@ -5,6 +5,7 @@
     "commits": [
       {
         "id": "ab06a042344dbd1c4af974ef393049b44ad0ae28",
+        "timestamp": 1649175909,
         "message": "feature 1, breaking change in footer",
         "body": "Body feature 1",
         "footers": [

.github/fixtures/test-from-context/context.json

@@ -5,6 +5,7 @@
     "commits": [
       {
         "id": "c7541276668616c136d12a9ccd87087314d66fb6",
+        "timestamp": 1649201113,
         "message": "add tests",
         "body": null,
         "footers": [],
@@ -63,6 +64,7 @@
       "commits": [
         {
           "id": "ce8cecc9834e5cbdb5b4e79c8260cace3c0dd949",
+          "timestamp": 1649201111,
           "message": "feat(gui): add feature 2\n",
           "group": null,
           "scope": null,
@@ -197,6 +199,7 @@
     "commits": [
       {
         "id": "ce8cecc9834e5cbdb5b4e79c8260cace3c0dd949",
+        "timestamp": 1649201111,
         "message": "add feature 2",
         "body": null,
         "footers": [],
@@ -309,6 +312,7 @@
       "commits": [
         {
           "id": "c6ba7fe73c3b639ff2f934f3f98e5f50350ab463",
+          "timestamp": 1649201108,
           "message": "Initial commit\n",
           "group": null,
           "scope": null,
@@ -493,6 +497,7 @@
     "commits": [
       {
         "id": "9c10e506bf103998e303d8164c7b4a1a841e2471",
+        "timestamp": 1649201109,
         "message": "add feature 1",
         "body": null,
         "footers": [],