Enable gn check for //third_party/openxr

gn check was failing because a header listed in sources
(src/src/loader/xr_generated_loader.h) didn't have the right name
(it should be .hpp, not .h).

Bug: 1108481
Change-Id: I7f0df8a8efcd1d8e0b82591fb63f9062713dc20a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2314163Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791058}

.gn

@@ -347,7 +347,6 @@ no_check_targets = [
   "//third_party/openscreen/src/osp/public:*",  # 1 error
   "//third_party/openscreen/src/osp:*",  # 13 errors
   "//third_party/openscreen/src/util:*",  # 29 errors
-  "//third_party/openxr:*",  # 1 error
   "//third_party/pdfium/samples:*",  # 1 error
   "//third_party/pdfium/third_party:*",  # 2 errors
   "//third_party/pdfium:*",  # 1 error

third_party/openxr/BUILD.gn

@@ -48,7 +48,7 @@ if (enable_openxr) {
       "src/src/loader/runtime_interface.cpp",
       "src/src/loader/runtime_interface.hpp",
       "src/src/loader/xr_generated_loader.cpp",
-      "src/src/loader/xr_generated_loader.h",
+      "src/src/loader/xr_generated_loader.hpp",
       "src/src/xr_generated_dispatch_table.c",
       "src/src/xr_generated_dispatch_table.h",
     ]