Removed unused zio_decompress_fail_fraction variable

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Alek Pinchuk <alek.pinchuk@connectwise.com>
Closes #17599

module/zfs/zio_compress.c

@@ -37,12 +37,6 @@
 #include <sys/zio_compress.h>
 #include <sys/zstd/zstd.h>
 
-/*
- * If nonzero, every 1/X decompression attempts will fail, simulating
- * an undetected memory error.
- */
-static unsigned long zio_decompress_fail_fraction = 0;
-
 /*
  * Compression vectors.
  */
@@ -171,15 +165,6 @@ zio_decompress_data(enum zio_compress c, abd_t *src, abd_t *dst,
 	else
 		err = ci->ci_decompress(src, dst, s_len, d_len, ci->ci_level);
 
-	/*
-	 * Decompression shouldn't fail, because we've already verified
-	 * the checksum.  However, for extra protection (e.g. against bitflips
-	 * in non-ECC RAM), we handle this error (and test it).
-	 */
-	if (zio_decompress_fail_fraction != 0 &&
-	    random_in_range(zio_decompress_fail_fraction) == 0)
-		err = SET_ERROR(EINVAL);
-
 	return (err);
 }