Flip --incompatible_remote_downloader_send_all_headers

Fixes bazelbuild#16356

RELNOTES[INC] --incompatible_remote_downloader_send_all_headers is flipped to true. See bazelbuild#16356 for details.

Author: Yannic

src/main/java/com/google/devtools/build/lib/remote/options/RemoteOptions.java

@@ -622,7 +622,7 @@ public RemoteOutputsStrategyConverter() {
 
   @Option(
       name = "incompatible_remote_downloader_send_all_headers",
-      defaultValue = "false",
+      defaultValue = "true",
       documentationCategory = OptionDocumentationCategory.REMOTE,
       effectTags = {OptionEffectTag.UNKNOWN},
       metadataTags = {OptionMetadataTag.INCOMPATIBLE_CHANGE},