docs: fix some doc strings

Signed-off-by: Jan Kowalleck <jan.kowalleck@gmail.com>

cyclonedx/validation/__init__.py

@@ -53,8 +53,8 @@ def validate_str(self, data: str) -> Optional[ValidationError]:
 
         :param data: the data string to validate
         :return: validation error
-        :retval None: if `data` is valid
-        :retval ValidationError:  if `data` is invalid
+        :retval None: if ``data`` is valid
+        :retval ValidationError:  if ``data`` is invalid
         """
         ...
 
@@ -69,19 +69,19 @@ def __init__(self, schema_version: 'SchemaVersion') -> None:
 
     @property
     def schema_version(self) -> 'SchemaVersion':
-        """get the schema version."""
+        """Get the schema version."""
         return self.__schema_version
 
     @property
     @abstractmethod
     def output_format(self) -> OutputFormat:
-        """get the format."""
+        """Get the format."""
         ...
 
     @property
     @abstractmethod
     def _schema_file(self) -> Optional[str]:
-        """get the schema file according to schema version."""
+        """Get the schema file according to schema version."""
         ...
 
 
@@ -105,7 +105,7 @@ def make_schemabased_validator(output_format: OutputFormat, schema_version: 'Sch
 
 def make_schemabased_validator(output_format: OutputFormat, schema_version: 'SchemaVersion'
                                ) -> 'BaseSchemabasedValidator':
-    """get the default Schema-based Validator for a certain :class:``OutputFormat``.
+    """Get the default Schema-based Validator for a certain :class:`OutputFormat`.
 
     Raises error when no instance could be made.
     """