go.mod: keep replace directives in same part of file

This commit moves replace directives to consistently be defined in the
same place of go.mod rather than being split between other directives
(like exclude).

go.mod

@@ -743,6 +743,15 @@ replace (
 	go.opentelemetry.io/collector/service => github.com/grafana/opentelemetry-collector/service v0.0.0-20231018134914-c0109e052230
 )
 
+replace github.com/github/smimesign => github.com/grafana/smimesign v0.2.1-0.20220408144937-2a5adf3481d3
+
+// Replacing for an internal for with a bugfix for delta histograms, https://github.com/grafana/stackdriver_exporter/pull/1
+// Moving back to upstream is being tracked in an internal issue
+replace github.com/prometheus-community/stackdriver_exporter => github.com/grafana/stackdriver_exporter v0.0.0-20240228143257-3a2c9acef5a2
+
+// Submodules.
+replace github.com/grafana/alloy/syntax => ./syntax
+
 // Required to avoid an ambiguous import with github.com/tencentcloud/tencentcloud-sdk-go
 exclude github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/common v1.0.194
 
@@ -752,12 +761,3 @@ exclude (
 	k8s.io/client-go v8.0.0+incompatible
 	k8s.io/client-go v12.0.0+incompatible
 )
-
-replace github.com/github/smimesign => github.com/grafana/smimesign v0.2.1-0.20220408144937-2a5adf3481d3
-
-// Replacing for an internal for with a bugfix for delta histograms, https://github.com/grafana/stackdriver_exporter/pull/1
-// Moving back to upstream is being tracked in an internal issue
-replace github.com/prometheus-community/stackdriver_exporter => github.com/grafana/stackdriver_exporter v0.0.0-20240228143257-3a2c9acef5a2
-
-// Submodules.
-replace github.com/grafana/alloy/syntax => ./syntax