glossary: Fix PDB tooltip text

The tooltip text for the Pod Disruption Budget term renders incorrectly due to
the templating of the "Pod" term within the `short_description`. This can be
observed by hovering the cursor over the "PodDisruptionBudget" term on the
following page: https://kubernetes.io/docs/concepts/scheduling-eviction/node-pressure-eviction/

Fix the issue by replacing the templated text with the literal word "Pod". Also,
slightly modify the wording to align with the full description on the following page:
https://kubernetes.io/docs/concepts/workloads/pods/disruptions/#pod-disruption-budgets

Author: disposedtrolley

content/en/docs/reference/glossary/pod-disruption-budget.md

@@ -4,7 +4,7 @@ title: Pod Disruption Budget
 full-link: /docs/concepts/workloads/pods/disruptions/
 date: 2019-02-12
 short_description: >
- An object that limits the number of {{< glossary_tooltip text="Pods" term_id="pod" >}} of a replicated application, that are down simultaneously from voluntary disruptions.
+ An object that limits the number of Pods of a replicated application that are down simultaneously from voluntary disruptions.
 
 aka:
  - PDB
@@ -17,8 +17,8 @@ tags:
 
  A [Pod Disruption Budget](/docs/concepts/workloads/pods/disruptions/) allows an 
  application owner to create an object for a replicated application, that ensures 
- a certain number or percentage of Pods with an assigned label will not be voluntarily
- evicted at any point in time.
+ a certain number or percentage of {{< glossary_tooltip text="Pods" term_id="pod" >}}
+ with an assigned label will not be voluntarily evicted at any point in time.
 
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