Remove json render metrics from the environment

This json can break some tools that try to pass or evaluate the
environment and the original use case has been superceded by sentry
reporting.

Signed-off-by: Ryan Bottriell <rbottriell@ilm.com>

crates/spfs-cli/cmd-enter/Cargo.toml

@@ -15,7 +15,6 @@ sentry = ["spfs-cli-common/sentry"]
 anyhow = { workspace = true }
 clap = { workspace = true }
 nix = { workspace = true }
-serde_json = { workspace = true }
 spfs = { path = "../../spfs" }
 spfs-cli-common = { path = "../common" }
 tokio = { version = "1.20", features = ["rt", "rt-multi-thread"] }

crates/spfs-cli/cmd-enter/src/cmd_enter.rs

@@ -14,7 +14,6 @@ use anyhow::{Context, Result};
 use clap::{Args, Parser};
 #[cfg(feature = "sentry")]
 use cli::configure_sentry;
-use serde_json::json;
 use spfs::monitor::SPFS_MONITOR_FOREGROUND_LOGGING_VAR;
 use spfs::storage::fs::RenderSummary;
 use spfs_cli_common as cli;
@@ -245,15 +244,9 @@ impl CmdEnter {
             .context("Failed to execute runtime command")
     }
 
-    fn report_render_summary(&self, render_summary: RenderSummary, render_time: f64) {
+    #[cfg_attr(not(feature = "sentry"), allow(unused))]
+    fn report_render_summary(&self, _render_summary: RenderSummary, render_time: f64) {
         if self.enter.metrics_in_env {
-            // The render summary data is put into a json blob in a
-            // environment variable for other, non-spfs, programs to
-            // access.
-            std::env::set_var(
-                "SPFS_METRICS_RENDER_REPORT",
-                format!("{}", json!(render_summary)),
-            );
             // The render time is put into environment variables for
             // other, non-spfs, programs to access. If this command
             // has been run from spfs-run, then the sync time will