Fix AMD cpu detection.

Currently we take generic/default code-path on AMD due to misspelling.
Mostly helps with crc+memcpy:

name                            old speed               new speed               delta
BM_Memcpy/1                      156MB/s ± 1%            156MB/s ± 1%     ~           (p=0.563 n=18+18)
BM_Memcpy/100                   6.38GB/s ± 1%           6.50GB/s ± 1%   +1.89%        (p=0.000 n=19+19)
BM_Memcpy/10000                 14.6GB/s ± 1%           21.7GB/s ± 0%  +49.01%        (p=0.000 n=20+19)
BM_Memcpy/500000                13.5GB/s ± 1%           19.9GB/s ± 0%  +47.35%        (p=0.000 n=18+17)

PiperOrigin-RevId: 490572650
Change-Id: Id7901321a23262c0ab62a2d82fae86cf42acf16d

absl/crc/internal/cpu_detect.cc

@@ -64,7 +64,7 @@ Vendor GetVendor() {
   vendor.append(reinterpret_cast<char*>(&cpu_info[2]), 4);
   if (vendor == "GenuineIntel") {
     return Vendor::kIntel;
-  } else if (vendor == "AuthenticAmd") {
+  } else if (vendor == "AuthenticAMD") {
     return Vendor::kAmd;
   } else {
     return Vendor::kUnknown;