Update image urls to non-transparent version.

[tomislavhofman]

Updated image urls to use non-transparent ones as per #6883

Resolves #6883

[codecov]

Codecov Report

Merging #6944 into 3.x will increase coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                3.x    #6944   +/-   ##
=========================================
  Coverage     99.63%   99.64%           
- Complexity     6666     6667    +1     
=========================================
  Files           742      742           
  Lines         47220    47220           
  Branches       6367     6367           
=========================================
+ Hits          47049    47051    +2     
+ Misses           54       50    -4     
- Partials        117      119    +2     

Impacted Files	Coverage Δ	Complexity Δ
...in/java/io/reactivex/rxjava3/core/Completable.java	100.00% <ø> (ø)	140.00 <0.00> (ø)
.../main/java/io/reactivex/rxjava3/core/Flowable.java	100.00% <ø> (ø)	595.00 <0.00> (ø)
src/main/java/io/reactivex/rxjava3/core/Maybe.java	100.00% <ø> (ø)	214.00 <0.00> (ø)
...ain/java/io/reactivex/rxjava3/core/Observable.java	100.00% <ø> (ø)	565.00 <0.00> (ø)
...rc/main/java/io/reactivex/rxjava3/core/Single.java	100.00% <ø> (ø)	196.00 <0.00> (ø)
...activex/rxjava3/flowables/ConnectableFlowable.java	100.00% <ø> (ø)	12.00 <0.00> (ø)
...operators/flowable/BlockingFlowableMostRecent.java	100.00% <ø> (ø)	2.00 <0.00> (ø)
...ernal/operators/flowable/BlockingFlowableNext.java	98.36% <ø> (ø)	2.00 <0.00> (ø)
...ators/observable/BlockingObservableMostRecent.java	100.00% <ø> (ø)	2.00 <0.00> (ø)
...l/operators/observable/BlockingObservableNext.java	98.36% <ø> (ø)	2.00 <0.00> (ø)
... and 22 more

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[akarnokd]

Thanks. The new v3 images load in properly.

[tomislavhofman]

Glad to help.