Drop ABSL_RANDOM_HWAES_FLAGS compiler flags

Older CPUs that do not have SSE4.1 would crash with the Ruby native gem
due to an illegal instruction exception.

The Abseil random library isn't being used at the moment
(#26476), and there's no reason gRPC
needs to force SSE4.1 instructions on all platforms at the moment. There
are other hardware-specific issues that need to be ironed out for this
to work: #26479

When the `-msse4` compiler flag was enabled, the Abseil code started
using the `pinsrb` instruction:

```
$ elfx86exts abseil-cpp/absl/time/internal/cctz/src/time_zone_libc.o
MODE64 (ret)
CMOV (cmovne)
SSE2 (movdqa)
SSE41 (pinsrb)
SSE1 (movaps)
CPU Generation: Penryn
```

Closes #27095

build_handwritten.yaml

@@ -165,7 +165,7 @@ configs:
       UBSAN_OPTIONS: halt_on_error=1:print_stacktrace=1:suppressions=test/core/util/ubsan_suppressions.txt
 defaults:
   abseil:
-    CPPFLAGS: -g $(ABSL_RANDOM_HWAES_FLAGS) -Ithird_party/abseil-cpp
+    CPPFLAGS: -Ithird_party/abseil-cpp
   ares:
     CFLAGS: -g
     CPPFLAGS: -Ithird_party/cares -Ithird_party/cares/cares -fvisibility=hidden -D_GNU_SOURCE

templates/Makefile.template

@@ -74,14 +74,6 @@
   SYSTEM = MINGW32
   endif
 
-  # Basic machine detection
-  HOST_MACHINE = $(shell uname -m)
-  ifeq ($(HOST_MACHINE),x86_64)
-  HOST_IS_X86_64 = true
-  else
-  HOST_IS_X86_64 = false
-  endif
-
   MAKEFILE_PATH := $(abspath $(lastword $(MAKEFILE_LIST)))
   ifndef BUILDDIR
   BUILDDIR_ABSOLUTE = $(patsubst %/,%,$(dir $(MAKEFILE_PATH)))
@@ -441,11 +433,6 @@
 
   GRPC_ABSEIL_DEP = $(LIBDIR)/$(CONFIG)/libgrpc_abseil.a
   GRPC_ABSEIL_MERGE_LIBS = $(LIBDIR)/$(CONFIG)/libgrpc_abseil.a
-  ifeq ($(HOST_IS_X86_64),true)
-  ABSL_RANDOM_HWAES_FLAGS = -maes -msse4
-  else
-  ABSL_RANDOM_HWAES_FLAGS =
-  endif
 
   # Setup re2 dependency