fix argument mismatches in Paint JNI

Paint.getTextRunCursor() no longer has a "flags" argument on the Java
side. The native side, however, still had the argument, and was being
called with misaligned arguments, causing all manner of madcap fun.

Also, the version of Paint.getTextRunCursor() that took String as an
argument needed to lose the "flags" argument, as well, to prevent an
infinite loop in the CharSequence version of the function, which was
supposed to be calling the String version but was actually calling
itself.

Bug: 8201224
Change-Id: Iad0dabaf81185f29a082566cc64590f2ba9bc31c