[Doc] Fix typo. NFC

Fixes llvm#56429

Author: phoebewang

llvm/docs/LangRef.rst

@@ -2245,7 +2245,7 @@ example:
     about the range of vscale.
 ``"min-legal-vector-width"="<size>"``
     This attribute indicates the minimum legal vector width required by the
-    calling conversion. It is the maximum width of vector arguments and
+    calling convension. It is the maximum width of vector arguments and
     returnings in the function and functions called by this function. Because
     all the vectors are supposed to be legal type for compatibility.
     Backends are free to ignore the attribute if they don't need to support