chore: fix filenames to avoid import failures

Running `go get github.com/prometheus-operator/prometheus@v0.69.0` fails
with:

```
...
not found: create zip:
pkg/prometheus/testdata/TSDB_config_<_v2.39.0.golden: malformed file
path "pkg/prometheus/testdata/TSDB_config_<_v2.39.0.golden": invalid
char '<'
pkg/prometheus/testdata/TSDB_config_>=_v2.39.0.golden: malformed file
path "pkg/prometheus/testdata/TSDB_config_>=_v2.39.0.golden": invalid
char '>'
```

This commit renames the problematic golden files to avoid characters
which aren't supported by the checksum database.

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

pkg/prometheus/promcfg_test.go

@@ -4551,15 +4551,15 @@ func TestTSDBConfig(t *testing.T) {
 			tsdb: &monitoringv1.TSDBSpec{
 				OutOfOrderTimeWindow: monitoringv1.Duration("10m"),
 			},
-			golden: "TSDB_config_<_v2.39.0.golden",
+			golden: "TSDB_config_less_than_v2.39.0.golden",
 		},
 		{
 
 			name: "TSDB config >= v2.39.0",
 			tsdb: &monitoringv1.TSDBSpec{
 				OutOfOrderTimeWindow: monitoringv1.Duration("10m"),
 			},
-			golden: "TSDB_config_>=_v2.39.0.golden",
+			golden: "TSDB_config_greater_than_or_equal_to_v2.39.0.golden",
 		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {