Merge pull request #16888 from PolarisTLX/fix/flexbox-display-firefox

fix(seed): flex box challenges not displaying

seed/challenges/01-responsive-web-design/css-flexbox.json

@@ -35,6 +35,7 @@
       "challengeSeed": [
         "<style>",
         "  #box-container {",
+        "    height: 500px;",
         "    ",
         "  }",
         "  ",
@@ -197,6 +198,7 @@
         "<style>",
         "  #box-container {",
         "    display: flex;",
+        "    height: 500px;",
         "    ",
         "  }",
         "  #box-1 {",
@@ -351,6 +353,7 @@
         "<style>",
         "  #box-container {",
         "    display: flex;",
+        "    height: 500px;",
         "    ",
         "  }",
         "  #box-1 {",
@@ -665,8 +668,8 @@
         "  #box-container {",
         "    background: gray;",
         "    display: flex;",
-        "    ",
         "    height: 500px;",
+        "    ",
         "  }",
         "  #box-1 {",
         "    background-color: dodgerblue;",