GH-46169: [CI][R] Update R version to 4.5 due to 4.4 not being on APT repositories anymore (#46171)

### Rationale for this change

The [debian-12-docs](https://github.com/ursacomputing/crossbow/actions/runs/14477216662/job/40605633697) are failing due to R 4.4 missing from Debian repositories and https://cloud.r-project.org/bin/linux/ubuntu/ has also updated to 4.5

### What changes are included in this PR?

Update default R version on `.env` and ARG

### Are these changes tested?

Via CI (archery)

### Are there any user-facing changes?

No

* GitHub Issue: #46169

Authored-by: Raúl Cumplido <[email protected]>
Signed-off-by: Raúl Cumplido <[email protected]>

Author: raulcd

.env

@@ -72,7 +72,7 @@ PANDAS=latest
 PYTHON=3.9
 PYTHON_IMAGE_TAG=3.9
 PYTHON_ABI_TAG=cp39
-R=4.4
+R=4.5
 SPARK=master
 TURBODBC=latest
 

ci/docker/linux-apt-docs.dockerfile

@@ -18,7 +18,7 @@
 ARG base
 FROM ${base}
 
-ARG r=4.4
+ARG r=4.5
 
 ENV PUPPETEER_EXECUTABLE_PATH=/usr/bin/chromium
 

ci/docker/linux-apt-r.dockerfile

@@ -35,7 +35,7 @@ ENV LANG=C.UTF-8
 # Build R
 # [1] https://www.digitalocean.com/community/tutorials/how-to-install-r-on-ubuntu-18-04
 # [2] https://linuxize.com/post/how-to-install-r-on-ubuntu-18-04/#installing-r-packages-from-cran
-ARG r=4.4
+ARG r=4.5
 RUN apt-get update -y && \
     apt-get install -y \
         dirmngr \