debian: Bump kernel dependency to 6.0.0pureos2

Otherwise the new UCM will unconditionally favor wired microphone
input even if none is connected.

debian/control

@@ -20,7 +20,7 @@ Depends:
  ${germinate:Depends},
  ${misc:Depends},
 # Either hardware or emulator
- linux-image-librem5 (>= 5.16.11pureos2) <!pkg.librem5-base.nokernel>
+ linux-image-librem5 (>= 6.0.0pureos2) <!pkg.librem5-base.nokernel>
   | linux-image-amd64 <!pkg.librem5-base.nokernel>,
 Recommends:
  ${germinate:Recommends}