NoSourceSince Anti-Feature should only be added to index

Before, it was being added to the metadata, so that rewritemeta would
output it.

fdroid/fdroidserver!529
#508

tests/repo/index-v1.json

@@ -127,6 +127,9 @@
       }
     },
     {
+      "antiFeatures": [
+        "NoSourceSince"
+      ],
       "categories": [
         "Time"
       ],
@@ -180,6 +183,9 @@
     "com.politedroid": [
       {
         "added": 1498176000000,
+        "antiFeatures": [
+          "NoSourceSince"
+        ],
         "apkName": "com.politedroid_6.apk",
         "hash": "70c2f776a2bac38a58a7d521f96ee0414c6f0fb1de973c3ca8b10862a009247d",
         "hashType": "sha256",
@@ -204,6 +210,9 @@
       },
       {
         "added": 1498176000000,
+        "antiFeatures": [
+          "NoSourceSince"
+        ],
         "apkName": "com.politedroid_5.apk",
         "hash": "5bdbfa071cca4b8d05ced41d6b28763595d6e8096cca5bbf0f9253c9a2622e5d",
         "hashType": "sha256",
@@ -228,6 +237,9 @@
       },
       {
         "added": 1498176000000,
+        "antiFeatures": [
+          "NoSourceSince"
+        ],
         "apkName": "com.politedroid_4.apk",
         "hash": "c809bdff83715fbf919f3840ee09869b038e209378b906e135ee40d3f0e1f075",
         "hashType": "sha256",
@@ -266,6 +278,7 @@
         "added": 1498176000000,
         "antiFeatures": [
           "KnownVuln",
+          "NoSourceSince",
           "NonFreeAssets",
           "UpstreamNonFree"
         ],

tests/repo/index.xml

@@ -237,6 +237,7 @@
 		<tracker>https://github.com/miguelvps/PoliteDroid/issues</tracker>
 		<marketversion>1.5</marketversion>
 		<marketvercode>6</marketvercode>
+		<antifeatures>NoSourceSince</antifeatures>
 		<package>
 			<version>1.5</version>
 			<versioncode>6</versioncode>