fix(deps): update dependency @google-cloud/common to ^0.26.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	References
@​google-cloud/common	dependencies	minor	^0.25.0 -> ^0.26.0	source

---

Release Notes

googleapis/nodejs-common

v0.26.0

Compare Source

Implementation Changes

• fix(typescript): Make ResponseCallback match subtype (#​271)
• fix: Do not retry streaming POST requests. (#​268)
• Don't publish sourcemaps (#​256)

Dependencies

• chore: Remove 'is' dependency (#​270)
• chore(deps): update dependency sinon to v7 (#​267)
• chore(deps): update dependency typescript to ~3.1.0 (#​259)

Internal / Testing Changes

• chores(build): run codecov on continuous builds (#​276)
• chore: update new issue template (#​274)
• chore: re-enable codecov (#​266)
• test: move install to system tests, and other tsconfig cleanup (#​269)
• Update kokoro config (#​264)
• docs: Remove appveyor badge from readme (#​262)
• Update CI config (#​258)
• build: prevent system/sample-test from leaking credentials
• Update the kokoro config (#​254)
• test: remove appveyor config (#​253)
• Update CI config (#​252)

---

Renovate configuration

📅 Schedule: "after 9am and before 3pm" (UTC).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻️ Rebasing: Whenever PR is stale, or if you modify the PR title to begin with "rebase!".

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

This PR has been generated by Renovate Bot. View repository job log here.

[renovate]

PR has been edited

👷 This PR has received other commits, so Renovate will stop updating it to avoid conflicts or other problems. If you wish to abandon your changes and have Renovate start over then you can add the label rebase to this PR and Renovate will reset/recreate it.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@1943ecf). Click here to learn what that means.
The diff coverage is 98.58%.

@@            Coverage Diff            @@
##             master     #185   +/-   ##
=========================================
  Coverage          ?   99.25%           
=========================================
  Files             ?       19           
  Lines             ?     1476           
  Branches          ?        0           
=========================================
  Hits              ?     1465           
  Misses            ?       11           
  Partials          ?        0

Impacted Files	Coverage Δ
src/index.js	100% <ø> (ø)
src/instance-group.js	100% <100%> (ø)
src/autoscaler.js	100% <100%> (ø)
src/network.js	100% <100%> (ø)
src/snapshot.js	100% <100%> (ø)
src/rule.js	100% <100%> (ø)
src/firewall.js	100% <100%> (ø)
src/zone.js	100% <100%> (ø)
src/subnetwork.js	100% <100%> (ø)
src/disk.js	100% <100%> (ø)
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1943ecf...578ab5a. Read the comment docs.