[Core Graphics] Fix apinotes for CGPathCreateMutableCopy

CGPathCreateMutableCopy and CGPathCreateMutableCopyByTransformingPath
have 'self' type of CGPath, and thus must be imported as members of
CGPath proper, not CGMutablePath. Does so by following common naming
conventions for producing mutable copies.

Author: milseman

apinotes/CoreGraphics.apinotes

@@ -430,9 +430,9 @@ Functions:
 - Name: CGPathCreateCopyByTransformingPath
   SwiftName: CGPathRef.copy(self:using:)
 - Name: CGPathCreateMutableCopy
-  SwiftName: CGMutablePathRef.copy(self:)
+  SwiftName: CGPathRef.mutableCopy(self:)
 - Name: CGPathCreateMutableCopyByTransformingPath
-  SwiftName: CGMutablePathRef.copy(self:using:)
+  SwiftName: CGPathRef.mutableCopy(self:using:)
 - Name: CGPathEqualToPath
   SwiftName: CGPathRef.equalTo(self:_:)
 - Name: CGPathGetPathBoundingBox