test: Update Emscripten failures/passing

All tests should now have annotation for *why* they're ignored on emscripten. A
few tests no longer need such an annotation as well!

Closes #41299

src/test/run-pass/thinlto/thin-lto-inlines.rs

@@ -10,7 +10,7 @@
 
 // compile-flags: -Z thinlto -C codegen-units=8 -O
 // min-llvm-version 4.0
-// ignore-emscripten
+// ignore-emscripten can't inspect instructions on emscripten
 
 // We want to assert here that ThinLTO will inline across codegen units. There's
 // not really a great way to do that in general so we sort of hack around it by

src/test/run-pass/thinlto/thin-lto-inlines2.rs

@@ -12,7 +12,7 @@
 // aux-build:thin-lto-inlines-aux.rs
 // min-llvm-version 4.0
 // no-prefer-dynamic
-// ignore-emscripten
+// ignore-emscripten can't inspect instructions on emscripten
 
 // We want to assert here that ThinLTO will inline across codegen units. There's
 // not really a great way to do that in general so we sort of hack around it by