[RISCV] incorrect-extract-subvector-combine.ll - remove quotes around -mattr argument. NFC.

The unnecessary quotes prevents DOS scripts from executing the RUN line.

Author: RKSimon

llvm/test/CodeGen/RISCV/rvv/incorrect-extract-subvector-combine.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
-; RUN: llc -mtriple=riscv64 -mattr='+zve64f,+zvl512b' < %s | FileCheck %s
+; RUN: llc -mtriple=riscv64 -mattr=+zve64f,+zvl512b < %s | FileCheck %s
 
 ; Previously, an incorrect (extract_subvector (extract_subvector X, C), 0) DAG combine crashed
 ; this snippet.