chore: prepare to release tracing-flame 0.2 (#1786)

The current version of tracing-flame on crates.io relies on
tracing-subscriber 0.2. This release fixes that.

Author: davidbarsky

tracing-flame/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tracing-flame"
-version = "0.1.0"
+version = "0.2.0"
 authors = [
     "Jane Lusby <[email protected]>",
     "Tokio Contributors <[email protected]>"