Update key for newer cargo-release

Author: LegNeato

_build/release.toml

@@ -1,6 +1,6 @@
 no-dev-version = true
 pre-release-commit-message = "Release {{crate_name}} {{version}}"
-pro-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
+post-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
 tag-message = "Release {{crate_name}} {{version}}"
 pre-release-replacements = [
   {file="CHANGELOG.md", min=0, search="# master", replace="# master\n\n- Compatibility with the latest `juniper`.\n\n# [[{{version}}] {{date}}](https://github.com/graphql-rust/juniper/releases/tag/{{crate_name}}-{{version}})"},

juniper/release.toml

@@ -1,6 +1,6 @@
 no-dev-version = true
 pre-release-commit-message = "Release {{crate_name}} {{version}}"
-pro-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
+post-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
 tag-message = "Release {{crate_name}} {{version}}"
 pre-release-replacements = [
   # Juniper's changelog

juniper_codegen/release.toml

@@ -1,6 +1,6 @@
 no-dev-version = true
 pre-release-commit-message = "Release {{crate_name}} {{version}}"
-pro-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
+post-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
 tag-message = "Release {{crate_name}} {{version}}"
 pre-release-replacements = [
   {file="../juniper/Cargo.toml", min=0, search="juniper_codegen = \\{ version = \"[^\"]+\"", replace="juniper_codegen = { version = \"{{version}}\""},

juniper_graphql_ws/release.toml

@@ -1,6 +1,6 @@
 no-dev-version = true
 pre-release-commit-message = "Release {{crate_name}} {{version}}"
-pro-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
+post-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
 tag-message = "Release {{crate_name}} {{version}}"
 pre-release-replacements = [
   {file="src/lib.rs", min=0, search="docs.rs/juniper_graphql_ws/[a-z0-9\\.-]+", replace="docs.rs/juniper_graphql_ws/{{version}}"},

juniper_subscriptions/release.toml

@@ -1,6 +1,6 @@
 no-dev-version = true
 pre-release-commit-message = "Release {{crate_name}} {{version}}"
-pro-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
+post-release-commit-message = "Bump {{crate_name}} version to {{next_version}}"
 tag-message = "Release {{crate_name}} {{version}}"
 pre-release-replacements = [
   {file="../juniper_graphql_ws/Cargo.toml", min=0, search="juniper_subscriptions = \\{ version = \"[^\"]+\"", replace="juniper_subscriptions = { version = \"{{version}}\""},