Revert "loongarch64: Add loongarch64 architecture detection support."

This reverts commit 0648830632.

Reason for revert: Pending clarity on https://bugs.chromium.org/p/chromium/issues/detail?id=1361860

Original change's description:
> loongarch64: Add loongarch64 architecture detection support.
>
> Bug: 1361860
> Change-Id: I432208fd78fb99140a97b3979a257f4e2e513807
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3886536
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
> Reviewed-by: Brian Ryner <bryner@google.com>
> Reviewed-by: Gavin Mak <gavinmak@google.com>

Bug: 1361860
Change-Id: Icf9f88a7173d4d403f4846fe01342794a0f5db9e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4667669
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

cipd

@@ -79,9 +79,6 @@ if [ -z $ARCH ]; then
     riscv64)
       ARCH=riscv64
       ;;
-    loongarch64)
-      ARCH=loong64
-      ;;
     *)
       >&2 echo "UNKNOWN Machine architecture: ${UNAME}"
       exit 1

detect_host_arch.py

@@ -34,8 +34,6 @@ def HostArch():
     host_arch = 's390'
   elif host_arch.startswith('riscv'):
     host_arch = 'riscv64'
-  elif host_arch.startswith('loongarch64'):
-    host_arch = 'loong64'
 
   if host_arch == 'arm64':
     host_platform = platform.architecture()

gclient.py

@@ -1369,6 +1369,7 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
         'checkout_mac': 'mac' in self.target_os,
         'checkout_win': 'win' in self.target_os,
         'host_os': _detect_host_os(),
+
         'checkout_arm': 'arm' in self.target_cpu,
         'checkout_arm64': 'arm64' in self.target_cpu,
         'checkout_x86': 'x86' in self.target_cpu,
@@ -1377,7 +1378,6 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
         'checkout_ppc': 'ppc' in self.target_cpu,
         'checkout_s390': 's390' in self.target_cpu,
         'checkout_x64': 'x64' in self.target_cpu,
-        'checkout_loong64': 'loong64' in self.target_cpu,
         'host_cpu': detect_host_arch.HostArch(),
     }