Ports: Remove obsolete patch for the oksh port

The patch is not necessary anymore and breaks the build
now that LibC has isblank.

Ports/oksh/patches/implement_isblank.patch

@@ -1,16 +0,0 @@
-diff --git a/charclass.h b/charclass.h
-index 5edb2c1..af00709 100644
---- a/charclass.h
-+++ b/charclass.h
-@@ -7,6 +7,11 @@
- /*
-  * POSIX character class support for fnmatch() and glob().
-  */
-+int
-+isblank(int c)
-+{
-+	return (c == ' ' || c == '\t');
-+}
- static struct cclass {
- 	const char *name;
- 	int (*isctype)(int);