Rename case statement conditions to selectors.

The name conditions isn't quite correct for the case statement. This CL
updates the code to use selectors instead of conditions.

Change-Id: I98b8050b11e2328f97e4443469572ab47d7c1555
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/22520
Reviewed-by: David Neto <dneto@google.com>
diff --git a/src/reader/wgsl/parser_impl.cc b/src/reader/wgsl/parser_impl.cc
index e81ef0c..36d82e4 100644
--- a/src/reader/wgsl/parser_impl.cc
+++ b/src/reader/wgsl/parser_impl.cc
@@ -1813,14 +1813,14 @@
   auto stmt = std::make_unique<ast::CaseStatement>();
   stmt->set_source(source);
   if (t.IsCase()) {
-    auto cond = case_selectors();
+    auto selectors = case_selectors();
     if (has_error())
       return nullptr;
-    if (cond.empty()) {
-      set_error(peek(), "unable to parse case conditional");
+    if (selectors.empty()) {
+      set_error(peek(), "unable to parse case selectors");
       return nullptr;
     }
-    stmt->set_conditions(std::move(cond));
+    stmt->set_selectors(std::move(selectors));
   }
 
   t = next();