Revert of Rotate component updater CUP key to the 2017 key (ECDSA 7)

components/update_client/request_sender.cc

Index: components/update_client/request_sender.cc
diff --git a/components/update_client/request_sender.cc b/components/update_client/request_sender.cc
index 782ada6a270cee08d0a054daef9aaf502b6ce723..b99648a6c259a4239ccd617bfbacf9f5e48ba6bf 100644
--- a/components/update_client/request_sender.cc
+++ b/components/update_client/request_sender.cc
@@ -26,10 +26,10 @@
 namespace {
 
 // This is an ECDSA prime256v1 named-curve key.
-const int kKeyVersion = 7;
+const int kKeyVersion = 6;
 const char kKeyPubBytesBase64[] =
-    "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEj0QKufXIOBN30DtKeOYA5NV64FfY"
-    "HDou4sGqtcNUIlxpTzIbO45rB45QILhW6aDTwwjWLR1YCqpEAGICvFs8dQ==";
+    "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAECEDSRcZPKv8k4JEYbF7MJxxx56m+x8Z+svg5gB"
+    "mRX1J8A9DYRL6NvFkNcmcRtSNemUm7/iqrUnxaadkqcWSODw==";
 
 // The ETag header carries the ECSDA signature of the protocol response, if
 // signing has been used.