sha3: delete unused field

Change-Id: I7dcb8a5ee07cc39e0c503f211f8f77732f006ad6
Reviewed-on: https://go-review.googlesource.com/59170
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

sha3/sha3.go

@@ -42,9 +42,8 @@ type state struct {
 	storage [maxRate]byte
 
 	// Specific to SHA-3 and SHAKE.
-	fixedOutput bool            // whether this is a fixed-output-length instance
-	outputLen   int             // the default output size in bytes
-	state       spongeDirection // whether the sponge is absorbing or squeezing
+	outputLen int             // the default output size in bytes
+	state     spongeDirection // whether the sponge is absorbing or squeezing
 }
 
 // BlockSize returns the rate of sponge underlying this hash function.