fix: Improve spacing of dependency grid in starter detail page (gatsb…

…yjs#10131)

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The spacing in the dependency grid looked off to me, so I improved it a bit.

Before: 
<img width="1064" alt="screenshot 2018-11-26 at 13 58 19" src="https://user-images.githubusercontent.com/541628/49015578-cbfa7a00-f183-11e8-9ee0-2452f8c1c83d.png">

After: 
<img width="1079" alt="screenshot 2018-11-26 at 13 58 07" src="https://user-images.githubusercontent.com/541628/49015584-d157c480-f183-11e8-86de-b7c20bee71f8.png">

www/src/views/starter/details.js

@@ -80,11 +80,10 @@ const Details = ({
       <div
         css={{
           display: `grid`,
-          gridAutoRows: `50px`,
           marginBottom: rhythm(options.blockMarginBottom * 5),
           [presets.Desktop]: {
             gridTemplateColumns: `repeat(3, 1fr)`,
-            gridColumnGap: 20,
+            gridGap: 20,
           },
         }}
       >
@@ -100,7 +99,6 @@ const Details = ({
                   key={dep}
                   css={{
                     ...sharedStyles.truncate,
-                    marginBottom: `1rem`,
                   }}
                 >
                   <a href={`https://npm.im/${dep}`}>