Remove unused constant.

We never implemented psk_ke, so there's no need to define the constant.

Change-Id: I6e52596e1a2cf0b3db5e7cd96db6836f4290bf0b
Reviewed-on: https://boringssl-review.googlesource.com/22144
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/ssl/internal.h b/ssl/internal.h
index 881f930..fe37595 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -2628,7 +2628,6 @@
 };
 
 // From draft-ietf-tls-tls13-18, used in determining PSK modes.
-#define SSL_PSK_KE     0x0
 #define SSL_PSK_DHE_KE 0x1
 
 // From draft-ietf-tls-tls13-16, used in determining whether to respond with a