coverage: Remove tests/coverage-map/if.rs

There is another test named `if.rs` in `tests/coverage-map/status-quo/`, so
this test stands in the way of flattening that directory into its parent.

Fortunately both tests are more-or-less equivalent, so removing this one is
fine.

tests/coverage-map/if.cov-map

@@ -1,15 +0,0 @@
-Function name: if::main
-Raw bytes (28): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 03, 01, 02, 0c, 05, 02, 0d, 02, 06, 02, 02, 06, 00, 07, 07, 01, 05, 01, 02]
-Number of files: 1
-- file 0 => global file 1
-Number of expressions: 2
-- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
-- expression 1 operands: lhs = Counter(1), rhs = Expression(0, Sub)
-Number of file 0 mappings: 4
-- Code(Counter(0)) at (prev + 3, 1) to (start + 2, 12)
-- Code(Counter(1)) at (prev + 2, 13) to (start + 2, 6)
-- Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
-    = (c0 - c1)
-- Code(Expression(1, Add)) at (prev + 1, 5) to (start + 1, 2)
-    = (c1 + (c0 - c1))
-

tests/coverage-map/if.rs

@@ -1,9 +0,0 @@
-// compile-flags: --edition=2021
-
-fn main() {
-    let cond = std::env::args().len() == 1;
-    if cond {
-        println!("true");
-    }
-    println!("done");
-}