pvmfw: Delete U-Boot-based pvmfw.img prebuilt

Remove the prebuilt (and its metadata) as it stopped being packaged by
the build system once we replaced it with the pvmfw.img built from the
Rust source in the same directory, using Soong.

Bug: 237371962
Test: m pvmfw_img  # replacement
Change-Id: I9a3256f8f64321da969ecb0f5e150cc10decbddc

.prebuilt_info/prebuilt_info_pvmfw_pvmfw_img.asciipb

@@ -1,13 +0,0 @@
-drops {
-  android_build_drop {
-    build_id: "9110780"
-    target: "u-boot_pvmfw"
-    source_file: "pvmfw.img"
-  }
-  dest_file: "pvmfw/pvmfw.img"
-  version: ""
-  version_group: ""
-  git_project: "platform/packages/modules/Virtualization"
-  git_branch: "master"
-  transform: TRANSFORM_NONE
-}