Rename inihibit_union_abi_opt() to inihibits_union_abi_opt()

The present tense makes it read more naturally at use site i.e.
"this repr _inhibits_ optimizations"

compiler/rustc_abi/src/lib.rs

@@ -155,7 +155,7 @@ impl ReprOptions {
     }
 
     /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
-    pub fn inhibit_union_abi_opt(&self) -> bool {
+    pub fn inhibits_union_abi_opt(&self) -> bool {
         self.c()
     }
 }