QDecompressHelper: add comment for translators in readBrotli()

Spotted by Friedemann Kleint in code review.

Amends 763c47e.

Pick-to: 6.9
Change-Id: I3092c51964c167da30b6d1400ab2ba1e2f4df829
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/network/access/qdecompresshelper.cpp

@@ -720,6 +720,7 @@ qsizetype QDecompressHelper::readBrotli(char *data, const qsizetype maxSize)
         switch (result) {
         Q_UNLIKELY_BRANCH
         case BROTLI_DECODER_RESULT_ERROR:
+            //: Brotli (compression algorithm) decoding error, e.g. corrupted input or memory allocation problem.
             errorStr = QCoreApplication::translate("QHttp", "Brotli error: %1")
                            .arg(QUtf8StringView{BrotliDecoderErrorString(
                                BrotliDecoderGetErrorCode(brotliDecoderState))});