fix minor typos (#294)

pep-0008.txt

@@ -466,7 +466,7 @@ Avoid extraneous whitespace in the following situations:
       Yes: spam(ham[1], {eggs: 2})
       No:  spam( ham[ 1 ], { eggs: 2 } )
 
-- Between a trailing comma and a following close parentheses. ::
+- Between a trailing comma and a following close parenthesis. ::
 
       Yes: foo = (0,)
       No:  bar = (0, )

pep-0225.txt

@@ -328,7 +328,7 @@ Some analysis are as follows:
 
 - The ``.op`` form is ambiguous: ``1.+a`` would be different from ``1 .+a``.
 - The bracket type operators are most favorable when standing alone, but
-  not in formulas, as they interfere with visual parsing of parenthesis for
+  not in formulas, as they interfere with visual parsing of parentheses for
   precedence and function argument. This is so for ``(op)`` and ``[op]``, and
   somewhat less so for ``{op}`` and ``<op>``.
 

pep-0308.txt

@@ -174,7 +174,7 @@ Alternatives
 
         <condition> then <expression1> else <expression2>
 
-    The advantages are simple visual parsing, no required parenthesis,
+    The advantages are simple visual parsing, no required parentheses,
     no change in the semantics of existing keywords, not as likely
     as the proposal to be confused with statement syntax, and does
     not further overload the colon.  The disadvantage is the

pep-0436.txt

@@ -350,7 +350,7 @@ value in the generated C code.  Few default values are permitted,
 owing to this manual translation step.
 
 If this were a Python function declaration, a parameter declaration
-would be delimited by either a trailing comma or an ending parentheses.
+would be delimited by either a trailing comma or an ending parenthesis.
 However, Argument Clinic uses neither; parameter declarations are
 delimited by a newline.  A trailing comma or right parenthesis is not
 permitted.

pep-0498.txt

@@ -649,7 +649,7 @@ Lambdas inside expressions
 --------------------------
 
 Because lambdas use the ``':'`` character, they cannot appear outside
-of parenthesis in an expression. The colon is interpreted as the start
+of parentheses in an expression. The colon is interpreted as the start
 of the format specifier, which means the start of the lambda
 expression is seen and is syntactically invalid. As there's no
 practical use for a plain lambda in an f-string expression, this is