[expected.bad.void] Fix syntax error in bad_expected_access<void> (#7529)

Introduced by commit 8c99744

Author: Bronek

source/utilities.tex

@@ -7392,7 +7392,7 @@
     bad_expected_access() noexcept;
     bad_expected_access(const bad_expected_access&) noexcept;
     bad_expected_access(bad_expected_access&&) noexcept;
-    bad_expected_access& operator=(const bad_expected_access& noexcept);
+    bad_expected_access& operator=(const bad_expected_access&) noexcept;
     bad_expected_access& operator=(bad_expected_access&&) noexcept;
     ~bad_expected_access();