cmd/go: remove redundant AVX regex in security flag checks

Remove "-m(no-)?avx[0-9a-z]*" from validCompilerFlags in security.go,
because "-m(no-)?avx[0-9a-z.]*" (see line 108) already covers its
matching range.

Change-Id: Ic86a45eefa7639ed3a8cdee95f08021d9515678e
Reviewed-on: https://go-review.googlesource.com/c/go/+/717740
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

Author: mohanson

src/cmd/go/internal/work/security.go

@@ -100,7 +100,6 @@ var validCompilerFlags = []*lazyregexp.Regexp{
 	re(`-m(abi|arch|cpu|fpu|simd|tls-dialect|tune)=([^@\-].*)`),
 	re(`-m(no-)?v?aes`),
 	re(`-marm`),
-	re(`-m(no-)?avx[0-9a-z]*`),
 	re(`-mcmodel=[0-9a-z-]+`),
 	re(`-mfloat-abi=([^@\-].*)`),
 	re(`-m(soft|single|double)-float`),