strings: delete unused constant

Change-Id: I235c5bc7ce598047eccc1518984dd27f568046a2
Reviewed-on: https://go-review.googlesource.com/82776
Run-TryBot: Caleb Spare <cespare@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/strings/builder.go

@@ -28,8 +28,6 @@ func (b *Builder) Len() int { return len(b.buf) }
 // Reset resets the Builder to be empty.
 func (b *Builder) Reset() { b.buf = nil }
 
-const maxInt = int(^uint(0) >> 1)
-
 // grow copies the buffer to a new, larger buffer so that there are at least n
 // bytes of capacity beyond len(b.buf).
 func (b *Builder) grow(n int) {