RISC-V: tidying: Fix separation of I-related extensions

The author intended to split:

1.  Former "I" extensions
2.  Other "I"-related extensions

but incorrectly separated between "Zihpm" (a supplement of "Zicntr" which is
a former "I" extension) and "Zifencei" (a former "I" extension) while the
author intended making a separation between "Zifencei" and "Zihintpause"
(not a part of "I").

This commit fixes the separation.

library/stdarch/crates/std_detect/src/detect/arch/riscv.rs

@@ -109,10 +109,10 @@ features! {
     @FEATURE: #[unstable(feature = "stdarch_riscv_feature_detection", issue = "111192")] zihpm: "zihpm";
     without cfg check: true;
     /// "Zihpm" Extension for Hardware Performance Counters
-
     @FEATURE: #[unstable(feature = "stdarch_riscv_feature_detection", issue = "111192")] zifencei: "zifencei";
     without cfg check: true;
     /// "Zifencei" Extension for Instruction-Fetch Fence
+
     @FEATURE: #[unstable(feature = "stdarch_riscv_feature_detection", issue = "111192")] zihintpause: "zihintpause";
     without cfg check: true;
     /// "Zihintpause" Extension for Pause Hint