coverage: Tweak individual tests to be unaffected by rustfmt

Some of these tests use non-standard formatting that we can simulate by
strategically adding `//` line comments.

One contains `where` clauses that would be split across multiple lines, which
we can keep on one line by moving the bounds to the generic type instead.

tests/coverage/conditions.coverage

@@ -49,6 +49,7 @@
    LL|      1|        if countdown > 7 {
    LL|      1|            countdown -= 4;
    LL|      1|        }
+   LL|       |        //
    LL|      0|        else if countdown > 2 {
    LL|      0|            if countdown < 1 || countdown > 5 || countdown != 9 {
    LL|      0|                countdown = 0;