Fix related;

api/lovr/graphics/Buffer/getLength.lua

@@ -10,7 +10,7 @@ return {
     }
   },
   related = {
-    'lovr.graphics.getSize',
-    'lovr.graphics.getStride'
+    'Buffer:getSize',
+    'Buffer:getStride'
   }
 }

api/lovr/graphics/Buffer/getSize.lua

@@ -10,7 +10,7 @@ return {
     }
   },
   related = {
-    'lovr.graphics.getLength',
-    'lovr.graphics.getStride'
+    'Buffer:getLength',
+    'Buffer:getStride'
   }
 }

api/lovr/graphics/Buffer/getStride.lua

@@ -13,7 +13,7 @@ return {
     // TODO zero-stride and straddled-stride
   ]],
   related = {
-    'lovr.graphics.getSize',
-    'lovr.graphics.getLength'
+    'Buffer:getSize',
+    'Buffer:getLength'
   }
 }