Fix jq comment line continuation in versions.sh (#754)

./versions.sh was failing with:
jq: error: syntax error, unexpected INVALID_CHARACTER,
expecting '|' or ',' or ')' at <top-level>, line 24, column 8

Keep the /o\ flourish in the jq comment, but avoid ending the line with
a bare backslash so jq does not treat the next line as a continuation.

Author: orgads

versions.sh

@@ -22,7 +22,7 @@ shell="$(
 							"windows.*" # windows, windows_x86_64, windows_x86_64-2012plus, etc
 						] | join("|")) + ")$")
 						and (
-							# a few things old enough we do not want anything to do with them /o\
+							# a few things old enough we do not want anything to do with them /o\.
 							test("^(" + ([
 								"debian[89].*",
 								"ubuntu1[0-9].*"