Correct the spelling of a file in libxslt's sources list

Not all sources lists have been kept up to date with code
movement/removal and it seems to make some isolate steps in
cq sad for some CLs (mine).

Change-Id: I1bef29f477965e254e955970b1ab2471eb956f66
Reviewed-on: https://chromium-review.googlesource.com/c/1288870
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602810}
diff --git a/third_party/libxslt/BUILD.gn b/third_party/libxslt/BUILD.gn
index de06534..5490b18 100644
--- a/third_party/libxslt/BUILD.gn
+++ b/third_party/libxslt/BUILD.gn
@@ -68,7 +68,7 @@
     "src/libxslt/xsltlocale.h",
     "src/libxslt/xsltutils.c",
     "src/libxslt/xsltutils.h",
-    "src/libxslt/xsltwin32config.h",
+    "src/libxslt/xsltwin32config.h.in",
     "win32/config.h",
   ]