Fix R-devel errors

[jimhester]

These are due to R-devel using an updated version of PCRE, which throws an error due to using \R inside a character class (which is invalid anyway).

Version: 1.0.3
Check: tests
Result: ERROR
     Running 'testthat.R' [16s/17s]
    Running the tests in 'tests/testthat.R' failed.
    Complete output:
     > library(testthat)
     > library(lintr)
     >
     > test_check("lintr")
     -- 1. Error: it returns the input trimmed strictly to max if no lints found (@te
     invalid regular expression '\[[^:]+:[[:digit:]]+:[[:digit:]]+:\]\([^)]+\)[[:space:]]\*(?:style|warning|error):\*[^\R]+\R[^\R]+\R[^\R]+\R'
     1: expect_equal(trim_output("testing a longer non_lint string", max = 7), "testing") at testthat/test-methods.R:10
     2: quasi_label(enquo(object), label, arg = "object")
     3: eval_bare(get_expr(quo), get_env(quo))
     4: trim_output("testing a longer non_lint string", max = 7)
     5: rex::re_matches(x, re, global = TRUE, locations = TRUE)
     6: mapply(process_matches, gregexpr(pattern = pattern, data, perl = TRUE, ...), data,
     SIMPLIFY = FALSE)
     7: gregexpr(pattern = pattern, data, perl = TRUE, ...)
    
     -- 2. Error: it returns the input trimmed to the last full lint if one exists wi
     invalid regular expression '\[[^:]+:[[:digit:]]+:[[:digit:]]+:\]\([^)]+\)[[:space:]]\*(?:style|warning|error):\*[^\R]+\R[^\R]+\R[^\R]+\R'
     1: expect_equal(trim_output(t1, max = 200), substr(t1, 1, 195)) at testthat/test-methods.R:14
     2: quasi_label(enquo(object), label, arg = "object")
     3: eval_bare(get_expr(quo), get_env(quo))
     4: trim_output(t1, max = 200)
     5: rex::re_matches(x, re, global = TRUE, locations = TRUE)
     6: mapply(process_matches, gregexpr(pattern = pattern, data, perl = TRUE, ...), data,
     SIMPLIFY = FALSE)
     7: gregexpr(pattern = pattern, data, perl = TRUE, ...)
    
     == testthat results ===========================================================
     [ OK: 544 | SKIPPED: 0 | WARNINGS: 2 | FAILED: 2 ]
     1. Error: it returns the input trimmed strictly to max if no lints found (@test-methods.R#10)
     2. Error: it returns the input trimmed to the last full lint if one exists within the max (@test-methods.R#14)
    
     Error: testthat unit tests failed
     Execution halted

[jimhester]

Fixed by 386e86f