Restore clang-format formatting.

As discussed in https://codereview.chromium.org/2556743002/,
formatting is strange "because clang-format tries to align
columns, even if there's only one row with aligned columns.
I agree that this looks weird, and it sounds like it will be
fixed."

Removing the "// clang-format off" section as it has a cost
since it requires developer to manually code format the region.

BUG=None

Review-Url: https://codereview.chromium.org/2563593004
Cr-Commit-Position: refs/heads/master@{#437521}

tools/gn/xcode_writer.cc

@@ -36,15 +36,10 @@ struct SafeEnvironmentVariableInfo {
   bool capture_at_generation;
 };
 
-// clang-format off
 SafeEnvironmentVariableInfo kSafeEnvironmentVariables[] = {
-    {"HOME", true},
-    {"LANG", true},
-    {"PATH", true},
-    {"USER", true},
-    {"TMPDIR", false},
+    {"HOME", true}, {"LANG", true},    {"PATH", true},
+    {"USER", true}, {"TMPDIR", false},
 };
-// clang-format on
 
 XcodeWriter::TargetOsType GetTargetOs(const Args& args) {
   const Value* target_os_value = args.GetArgOverride(variables::kTargetOs);