Fix incorrect pool assignment in dogstatsd/event, service_check (#1750)

### What does this PR do?

This commit corrects a small bug introduced in PR #1732. I have a
    notion of how to make these pool handles type-safe but that's an
    intrusive change I do not want to bundle here.

Author: blt

lading_payload/fuzz/Cargo.lock

@@ -143,7 +143,7 @@ impl fmt::Display for Event<'_> {
                     .expect("invalid tag key handle");
                 let value = self
                     .pools
-                    .randomstring
+                    .tag_value
                     .using_handle(tag.value)
                     .expect("invalid tag value handle");
                 write!(f, "{key}:{value}")?;

lading_payload/src/dogstatsd/event.rs

@@ -93,12 +93,12 @@ impl fmt::Display for ServiceCheck<'_> {
             for tag in tags {
                 let key = self
                     .pools
-                    .randomstring
+                    .tag_name
                     .using_handle(tag.key)
                     .expect("invalid tag key handle");
                 let value = self
                     .pools
-                    .tag_name
+                    .tag_value
                     .using_handle(tag.value)
                     .expect("invalid tag value handle");
                 write!(f, "{key}:{value}")?;