Ruby: Serialize severities as lowercase

ruby/extractor/src/diagnostics.rs

@@ -3,6 +3,7 @@ use std::io::Write;
 use std::path::PathBuf;
 /** SARIF severity */
 #[derive(Serialize)]
+#[serde(rename_all = "lowercase")]
 pub enum Severity {
     Error,
     Warning,

ruby/ql/integration-tests/all-platforms/diagnostics/syntax-error/diagnostics.expected

@@ -11,7 +11,7 @@
   },
   "markdownMessage": "A parse error occurred. Check the syntax of the file. If the file is invalid, correct the error or [exclude](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/customizing-code-scanning) the file from analysis.",
   "plaintextMessage": "A parse error occurred. Check the syntax of the file. If the file is invalid, correct the error or exclude the file from analysis.",
-  "severity": "Warning",
+  "severity": "warning",
   "source": {
     "extractorName": "ruby",
     "id": "ruby/parse-error",
@@ -34,7 +34,7 @@
   },
   "markdownMessage": "A parse error occurred (expected `end` symbol). Check the syntax of the file. If the file is invalid, correct the error or [exclude](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/customizing-code-scanning) the file from analysis.",
   "plaintextMessage": "A parse error occurred (expected end symbol). Check the syntax of the file. If the file is invalid, correct the error or exclude the file from analysis.",
-  "severity": "Warning",
+  "severity": "warning",
   "source": {
     "extractorName": "ruby",
     "id": "ruby/parse-error",

ruby/ql/integration-tests/all-platforms/diagnostics/unknown-encoding/diagnostics.expected

@@ -7,7 +7,7 @@
   },
   "markdownMessage": "Unknown character encoding `silly` in `#encoding:` [directive](https://docs.ruby-lang.org/en/master/syntax/comments_rdoc.html#label-encoding+Directive).",
   "plaintextMessage": "Unknown character encoding silly in #encoding: directive.",
-  "severity": "Warning",
+  "severity": "warning",
   "source": {
     "extractorName": "ruby",
     "id": "ruby/unknown-character-encoding",