cue/errors: remove unnecessary first slice length on list.Reset()

The convention way of reset any slice is to set the last slice length only.

Change-Id: I3847c764deac32b39fe81e7e7fb0c76da0648293
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/4640
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/cue/errors/errors.go b/cue/errors/errors.go
index 9d13be0..f57aa66 100644
--- a/cue/errors/errors.go
+++ b/cue/errors/errors.go
@@ -271,7 +271,7 @@
 }
 
 // Reset resets an List to no errors.
-func (p *list) Reset() { *p = (*p)[0:0] }
+func (p *list) Reset() { *p = (*p)[:0] }
 
 // List implements the sort Interface.
 func (p list) Len() int      { return len(p) }