doc: fix typo

The document `doc/go_spec.html` uses "preceeding" instead of the word
"preceding" in one place.

Fixed another occurrence in `src/go/types/typexpr.go`.

Change-Id: Ic67f62026b5c9d002c5c5632299f14ecac8b02ae
Reviewed-on: https://go-review.googlesource.com/12354Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go_spec.html

@@ -2090,7 +2090,7 @@ Receiver     = Parameters .
 </pre>
 
 <p>
-The receiver is specified via an extra parameter section preceeding the method
+The receiver is specified via an extra parameter section preceding the method
 name. That parameter section must declare a single parameter, the receiver.
 Its type must be of the form <code>T</code> or <code>*T</code> (possibly using
 parentheses) where <code>T</code> is a type name. The type denoted by <code>T</code> is called

src/go/types/typexpr.go

@@ -151,7 +151,7 @@ func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast
 
 	if recvPar != nil {
 		// recv parameter list present (may be empty)
-		// spec: "The receiver is specified via an extra parameter section preceeding the
+		// spec: "The receiver is specified via an extra parameter section preceding the
 		// method name. That parameter section must declare a single parameter, the receiver."
 		var recv *Var
 		switch len(recvList) {