Add test caes for a minority language using Bengali

U+0985 BENGALI LETTER A followed by U+09D7 BENGALI AU LENGTH MARK.
According to Bobby de Vos on the mailing list, this results in a dotted
circle with most shaping engines, but is a legitimate sequence in this
minority language.

We reached the consensus on the list to NOT implement dotted-circle
in HarfBuzz.

test/shaping/texts/in-tree/shaper-indic/indic/script-bengali/misc/misc.txt

@@ -46,3 +46,4 @@
 র্ভ
 ৰ্ভ
 ৱ্ভ
+অৗ