Dockerfile: Update dates to make tests work again

Date earlier than 2022/05/19 produce an error:

  + update-kernel -v -f --headers
  Running kernel: 5.17.15-un-def-alt1 is not from package
  Checking for available std-def kernel packages...
  Latest kernel is kernel-image-std-def-5.15.40-alt1
  ATTENTION: Selected kernel is 1 months old.
  Kernel std-def version 5.15.40-alt1 has 43 external modules. Use -i to select what to install.
  Try to install new kernel kernel-image-std-def-5.15.40-alt1 and update its modules [Y/n]? yes
  + apt-get install -o APT::Install::Virtual=true -y kernel-image-std-def#2:5.15.40-alt1:sisyphus+300020.100.1.1@1652646109 kernel-headers-std-def kernel-headers-modules-std-def
  Reading Package Lists...
  Building Dependency Tree...
  Some packages could not be installed. This may mean that you have
  requested an impossible situation or if you are using the unstable
  distribution that some required packages have not yet been created
  or been moved out of Incoming.
  The following information may help to resolve the situation:

  The following packages have unmet dependencies:
    kernel-headers-modules-std-def: Depends: gcc11
  E: Broken packages
  update-kernel: failed to install kernel-image-std-def-2:5.15.40-alt1:sisyphus+300020.100.1.1@1652646109 with modules
  The command '/bin/bash -xec toilet -w 150 First install &&     update-kernel -v -f --headers &&     ls -l /boot/vmlinuz /boot/vmlinuz-std-def /boot/initrd.img /boot/initrd-std-def.img &&     ls -l /boot/$(readlink /boot/vmlinuz)' returned a non-zero code: 1
  make: *** [Makefile:8: docker-build] Error 1

Signed-off-by: Vitaly Chikunov <vt@altlinux.org>

Dockerfile

@@ -7,8 +7,8 @@ ENV UPDATE_KERNEL_SYS_FLAVOUR=std-def
 
 ARG branch=sisyphus
 ARG repo=http://ftp.altlinux.org/pub/distributions/archive/$branch/date
-ARG a=2022/01/01
-ARG b=2022/02/02
+ARG a=2022/05/19
+ARG b=2022/06/12
 
 # Initialize the system and start from some arbitrary date.
 # update-kernel is installed just for dependencies.