Update bundle run command description to mention apps (#3454)

## Why
<!-- Why are these changes needed? Provide the context that the reviewer
might be missing.
For example, were there any decisions behind the change that are not
reflected in the code itself? -->

`databricks bundle run` can start a Databricks app, but `--help`
description does not mention that.

Author: anton-107

acceptance/bundle/help/bundle-run/output.txt

@@ -1,6 +1,6 @@
 
 >>> [CLI] bundle run --help
-Run the job or pipeline identified by KEY.
+Run the job, pipeline or app identified by KEY.
 
 The KEY is the unique identifier of the resource to run. In addition to
 customizing the run using any of the available flags, you can also specify

acceptance/bundle/help/bundle/output.txt

@@ -24,7 +24,7 @@ Available Commands:
   generate    Generate bundle configuration
   init        Initialize using a bundle template
   open        Open a resource in the browser
-  run         Run a job or pipeline update
+  run         Run a job, pipeline update or app
   schema      Generate JSON Schema for bundle configuration
   summary     Summarize resources deployed by this bundle
   sync        Synchronize bundle tree to the workspace

cmd/bundle/run.go

@@ -86,8 +86,8 @@ func keyToRunner(b *bundle.Bundle, arg string) (run.Runner, error) {
 func newRunCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "run [flags] [KEY]",
-		Short: "Run a job or pipeline update",
-		Long: `Run the job or pipeline identified by KEY.
+		Short: "Run a job, pipeline update or app",
+		Long: `Run the job, pipeline or app identified by KEY.
 
 The KEY is the unique identifier of the resource to run. In addition to
 customizing the run using any of the available flags, you can also specify