Mixin: Change from Phlare to Pyroscope

[nlamirault]

Before this fix:

❯ mixtool generate all mixin.libsonnet
2023/08/31 10:02:14 RUNTIME ERROR: couldn't open import "dashboards/phlare-writes.libsonnet": no match locally or in the Jsonnet library paths
        dashboards.libsonnet:2:2-45     $
        mixin.libsonnet:2:2-31  $
        2:16-40 thunk <mixin> from <$>
        4:21-26 thunk from <$>
        <std>:1548:21-22        thunk from <function <anonymous>>
        <std>:1548:5-32 function <anonymous>
        4:4-47  $
        During evaluation

After:

❯ mixtool generate all mixin.libsonnet
❯ ls dashboards_out
pyroscope-reads.json    pyroscope-writes.json

[CLAassistant]

All committers have signed the CLA.

[cyriltovena]

LGTM