Remove stale platform-specific expectations

LayoutTests/platform/win/http/tests/multipart/invalid-image-data-standalone-expected.txt

-layer at (0,0) size 800x600
-  RenderView at (0,0) size 800x600
-layer at (0,0) size 800x600
-  RenderBlock {HTML} at (0,0) size 800x600
-    RenderBody {BODY} at (8,8) size 784x584
-      RenderBlock {P} at (0,0) size 784x40
-        RenderText {#text} at (0,0) size 51x19
-          text run at (0,0) width 51: "Test for "
-        RenderInline {I} at (0,0) size 779x39
-          RenderInline {A} at (0,0) size 305x19 [color=#0000EE]
-            RenderText {#text} at (51,0) size 305x19
-              text run at (51,0) width 305: "http://bugs.webkit.org/show_bug.cgi?id=13759"
-          RenderText {#text} at (356,0) size 779x39
-            text run at (356,0) width 4: " "
-            text run at (360,0) width 419: "REGRESSION (r20182-r20184): Incorrect rendering of multipart"
-            text run at (0,20) width 45: "images"
-        RenderText {#text} at (45,20) size 4x19
-          text run at (45,20) width 4: "."
-      RenderBlock {P} at (0,56) size 784x20
-        RenderText {#text} at (0,0) size 234x19
-          text run at (0,0) width 234: "There should be a green square below."
-      RenderBlock (anonymous) at (0,92) size 784x124
-        RenderPartObject {IFRAME} at (0,0) size 124x124 [border: (2px inset #000000)]
-          layer at (0,0) size 120x120
-            RenderView at (0,0) size 120x120
-          layer at (0,0) size 120x120
-            RenderBlock {HTML} at (0,0) size 120x120
-              RenderBody {BODY} at (0,0) size 120x120
-                RenderImage {IMG} at (0,0) size 100x100
-        RenderText {#text} at (0,0) size 0x0