text/template: removed truncation of context in error message

Fixes #27930

Change-Id: I31ad3fdb74d74152268c59ae4c651cc4c8c1716d
Reviewed-on: https://go-review.googlesource.com/c/142217Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/text/template/parse/parse.go

@@ -148,9 +148,6 @@ func (t *Tree) ErrorContext(n Node) (location, context string) {
 	}
 	lineNum := 1 + strings.Count(text, "\n")
 	context = n.String()
-	if len(context) > 20 {
-		context = fmt.Sprintf("%.20s...", context)
-	}
 	return fmt.Sprintf("%s:%d:%d", tree.ParseName, lineNum, byteNum), context
 }