Engine tests kvm=1 is required for some fuchsia (#169614)

Undoes some changes from #168106 as these tests are looking for a KVM
specifically for hardware accelerating the emulators. Tests are timing
out as "infra failures" and making the tree go red.

> KVM path /dev/kvm does not exist. Running without acceleration;
emulator will be extremely slow and may not establish a connection with
ffx in the allotted time.

engine/src/flutter/ci/builders/linux_fuchsia_tests.json

@@ -139,6 +139,7 @@
             "cas_archive": false,
             "drone_dimensions": [
                 "device_type=none",
+                "kvm=1",
                 "os=Linux"
             ],
             "gclient_variables": {
@@ -184,6 +185,7 @@
             "cas_archive": false,
             "drone_dimensions": [
                 "device_type=none",
+                "kvm=1",
                 "os=Linux"
             ],
             "gclient_variables": {
@@ -229,6 +231,7 @@
             "cas_archive": false,
             "drone_dimensions": [
                 "device_type=none",
+                "kvm=1",
                 "os=Linux"
             ],
             "gclient_variables": {