Run go mod tidy for monitor submodule

Run go mod tidy for monitor submodule

- remove tools.go that declares dependency on the crd/generator
  of controller tools [0]
- run go mod tidy

[0] this is a dependency that is not included in the build.
    the crd/generator package only exists in v1 version of
    controller-tools while controller-tools was declared in
    in v0.3.0.
    This prevented a successful go mod tidy run due to the
    conflict.

Issue-ID: MULTICLOUD-1530
Change-Id: If801420449f5f4d2458036f91a728cf9b0a40058
Signed-off-by: Fiete Ostkamp <fiete.ostkamp@telekom.de>