Fix runtime/printf lint

This Cl changes a hardcoded 4 to sizeof(buf) and re-enables the
runtime/printf lint.

Bug: dawn:1339
Change-Id: Iaeeab2bc0d500c1aa8085352e7b26febb810bd4e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/86863
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/dawn/CPPLINT.cfg

@@ -8,7 +8,6 @@ filter=-runtime/arrays
 filter=-runtime/explicit
 filter=-runtime/indentation_namespace
 filter=-runtime/int
-filter=-runtime/printf
 filter=-runtime/threadsafe_fn
 filter=-whitespace/blank_line
 filter=-whitespace/comments

src/dawn/tests/DawnTest.cpp

@@ -95,7 +95,7 @@ namespace {
             auto byteView = reinterpret_cast<const uint8_t*>(buffer + index);
             for (unsigned int b = 0; b < kBytes; ++b) {
                 char buf[4];
-                snprintf(buf, 4, "%02X ", byteView[b]);
+                snprintf(buf, sizeof(buf), "%02X ", byteView[b]);
                 result << buf;
             }
         }