[maven] remove validateSpec (#2614)

Aligning the option with CLI and Gradle Plugin, this keeps
`skipValidateSpec` and removes the redundant `validateSpec`.

modules/openapi-generator-maven-plugin/README.md

@@ -40,7 +40,6 @@ mvn clean compile
 :bulb: These **general** configurations should be in the same level
 
 - `inputSpec` - OpenAPI Spec file path
-- `validateSpec` - Whether or not to validate the input spec prior to generation. Invalid specifications will result in an error.
 - `language` - target generation language (deprecated, replaced by `generatorName` as values here don't represent only 'language' any longer)
 - `generatorName` - target generator name
 - `output` - target output path (default is `${project.build.directory}/generated-sources/openapi`. Can also be set globally through the `openapi.generator.maven.plugin.output` property)
@@ -51,13 +50,13 @@ mvn clean compile
 - `invokerPackage` - the package to use for the generated invoker objects
 - `modelNamePrefix` and `modelNameSuffix` - Sets the pre- or suffix for model classes and enums
 - `withXml` - enable XML annotations inside the generated models and API (only works with Java `language` and libraries that provide support for JSON and XML)
-- `configOptions` - a map of language-specific parameters. To show a full list of generator-specified parameters (options), please use `configHelp` (explained below) or refer to [generators docs](../../docs/generators.md)
+- `configOptions` - a map of language-specific parameters. To show a full list of generator-specified parameters (options), please use `configHelp` (explained below)
 - `configHelp` - dumps the configuration help for the specified library (generates no sources)
 - `ignoreFileOverride` - specifies the full path to a `.openapi-generator-ignore` used for pattern based overrides of generated outputs
 - `removeOperationIdPrefix` - remove operationId prefix (e.g. user_getName => getName)
 - `logToStderr` - write all log messages (not just errors) to STDOUT
 - `enablePostProcessFile` - enable file post-processing hook
-- `skipValidateSpec` - skip spec validation
+- `skipValidateSpec` - Whether or not to skip validating the input spec prior to generation. By default, invalid specifications will result in an error.
 - `generateAliasAsModel` - generate alias (array, map) as model
 - `generateApis` - generate the apis (`true` by default)
 - `generateApiTests` - generate the api tests (`true` by default. Only available if `generateApis` is `true`)

modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java

@@ -79,9 +79,6 @@ public class CodeGenMojo extends AbstractMojo {
     @Component
     private BuildContext buildContext = new DefaultBuildContext();
 
-    @Parameter(name="validateSpec", required = false, defaultValue = "true")
-    private Boolean validateSpec;
-
     @Parameter(name = "verbose", required = false, defaultValue = "false")
     private boolean verbose;
 
@@ -434,11 +431,6 @@ public void execute() throws MojoExecutionException {
 
             configurator.setVerbose(verbose);
 
-            // now override with any specified parameters
-            if (validateSpec != null) {
-                configurator.setValidateSpec(validateSpec);
-            }
-
             if (skipOverwrite != null) {
                 configurator.setSkipOverwrite(skipOverwrite);
             }