DrMemory: Remove a suppression of uninitialized error

In EmbeddedWorkerDispatcher::OnStartWorker,
start_data.pauseAfterDownloadMode used not to be initialized, but this was
already fixed at http://crrev.com/1713863002, so now we can remove the suppression.

BUG=387373

Review-Url: https://codereview.chromium.org/2139983002
Cr-Commit-Position: refs/heads/master@{#405072}

tools/valgrind/drmemory/suppressions_full.txt

@@ -1660,12 +1660,6 @@ name=bug_377728
 *!SpellcheckLanguage::SpellCheckWord
 *!SpellCheck::SpellCheckWord
 
-UNINITIALIZED READ
-name=bug_387373
-*!blink::WebEmbeddedWorkerImpl::startWorkerContext
-*!content::EmbeddedWorkerDispatcher::OnStartWorker
-*!EmbeddedWorkerMsg_StartWorker::Dispatch<>
-
 UNADDRESSABLE ACCESS
 name=bug_389132
 content.dll!crypto_kernel_do_load_cipher_type