spec: remove example explaining that type B0 and B0 are identical

Every few months we get a new error report claiming that there
is a typo in the spec related to this specific example. Clearly,
the fact that two types with the same identifier are identical
seems exceedingly obvious to readers; thus the example seems not
worth the trouble. Removing it.

For #9226.
For #22202.
For #22495.
For #23096.
For #23409.

There may be more.

Change-Id: I003ba79dc460ffb028a4ecb5f29efd60f2551912
Reviewed-on: https://go-review.googlesource.com/87417
Reviewed-by: Brad Fitzpatrick <[email protected]>
Reviewed-by: Rob Pike <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>

Author: griesemer

doc/go_spec.html

@@ -1,6 +1,6 @@
 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of January 9, 2018",
+	"Subtitle": "Version of January 11, 2018",
 	"Path": "/ref/spec"
 }-->
 
@@ -1495,7 +1495,7 @@ <h3 id="Type_identity">Type identity</h3>
 A3 and int
 A4, func(int, float64) *[]string, and A5
 
-B0, B0, and C0
+B0 and C0
 []int and []int
 struct{ a, b *T5 } and struct{ a, b *T5 }
 func(x int, y float64) *[]string, func(int, float64) (result *[]string), and A5