tests/float: Add new lexer test to test parsing of float without prefix.

Since automatically formatting tests with black, we have lost one line of
code coverage.  This adds an explicit test to ensure we are testing the
case that is no longer covered implicitly.

tests/float/lexer.py

@@ -0,0 +1,6 @@
+# since black code formatter does not allow leading decimal point with nothing
+# before it, we need to test it explicitly
+
+# fmt: off
+print(.1)
+# fmt: on