release: flipping deprecated features to fatal-by-default (#6509)

Making the following deprecated fields fatal-by-default
UNSUPPORTED_REST_LEGACY from config_source.proto
use_alpha from ext_authz.proto
enabled from route.proto
type from fault.proto
runtime_key from route.proto

Risk Level: High (first time using this process - it will likely cause problems for someone)
Testing: tests pass.
Docs Changes: n/a
Release Notes: no

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>

Mirrored from https://github.com/envoyproxy/envoy @ 19894aca58f21f73dfbdb939ce8597c58de8a574

envoy/config/filter/network/tcp_proxy/v2/tcp_proxy.proto

@@ -172,7 +172,8 @@ message TcpProxy {
   //   list of strings with each string in CIDR notation. Source and destination ports are
   //   specified as single strings containing a comma-separated list of ports and/or port ranges.
   //
-  DeprecatedV1 deprecated_v1 = 6 [deprecated = true];
+  // Deprecation pending https://github.com/envoyproxy/envoy/issues/4457
+  DeprecatedV1 deprecated_v1 = 6;
 
   // The maximum number of unsuccessful connection attempts that will be made before
   // giving up. If the parameter is not specified, 1 connection attempt will be made.