ci(dependabot): use increase-if-necessary versioning strategy for pip

Set versioning-strategy to increase-if-necessary for the pip ecosystem so
dependabot only bumps the version when required, reducing unnecessary
updates.

Author: csernazs

.github/dependabot.yml

@@ -12,6 +12,7 @@ updates:
           - "*"
 
   - package-ecosystem: "pip"
+    versioning-strategy: increase-if-necessary
     directory: "/"
     schedule:
       interval: "monthly"