[NFC] Remove trailing white spaces from llvm/docs/LangRef.rst

Author: shiltian

llvm/docs/LangRef.rst

@@ -13045,9 +13045,9 @@ This instruction requires several arguments:
    -  Caller and callee both have the calling convention ``fastcc`` or ``tailcc``.
    -  The call is in tail position (ret immediately follows call and ret
       uses value of call or is void).
-   -  Option ``-tailcallopt`` is enabled, ``llvm::GuaranteedTailCallOpt`` is 
+   -  Option ``-tailcallopt`` is enabled, ``llvm::GuaranteedTailCallOpt`` is
       ``true``, or the calling convention is ``tailcc``.
-   -  `Platform-specific constraints are met. 
+   -  `Platform-specific constraints are met.
       <CodeGenerator.html#tail-call-optimization>`_
 
 #. The optional ``notail`` marker indicates that the optimizers should not add